Runs well but it surges?

Hello, do you have a scan tool to look at some live engine data? Check the Long Term and Short-Term Fuel Trims at idle, if they are high positive numbers at idle, you may be dealing with a vacuum leak, raising the idle up to 2500rpm and the fuel trim numbers come down towards 0% is a good indicator of a vacuum leak. But looking through the live data should show something standing out if the issue is that bad. The fuel trims will tell you how much the ECM is compensating the air/fuel mixture due to it being off for whatever reason, start there, I'll see if service info has any type of values chart showing what good live data should read. Does it idle above 700 RPMs when hot as well?

https://www.2carpros.com/articles/automotive-engine-vacuum-leak-symptoms

These little engines react quite a bit to vacuum leaks, or any air leak that is past the Mass Air Flow sensor, any leaks beyond the MAF are considered "false air" and will affect the fuel trims, more at idle, so anything that looks odd we can look into further and see if that's what you're dealing with. Do you have a smoke machine?

Just yesterday I replaced a Purge valve hose going to the intake air boot that had caused the fuel trims to go up to +25% at idle. The engine was running extremely rich, it was so bad I couldn't even run the vehicle in the shop right with the vehicle at the open garage door. Once the repair was made, the Long Term went to +10% but the Short Term went to -10% so total fuel trim was close to 0%, the engine computer just needed to relearn its fuel strategy at that point.
Even a stuck open Purge valve is technically a vacuum leak due to the fresh air entering the Vent valve and through the Evap system.

This is a diagram of the Evap vapor management system. Another thing you can look into if you don't see anything obvious on the live engine data is the Mode 6 data, under the Mode 6 data any self-tests that have failed can also give you some direction, you'll need to dig through the scan tool a bit to find it sometimes, but it should be there for a 2010 OBD2 system.

Okay, let us know what you find.

Can you graph sensor signals with that scan tool? APP should set codes, yes, how was the Evap tested? I've seen the purge on these put on backwards before if it's been taken off before, very strange the hoses can hook up opposite, but it's possible and manifold vacuum pulls the valve open when on reversed.
Your Fuel trims look normal, even cylinder misfires can cause fuel trims to go either direction. You could try graphing the APP, looking for dropouts and correct voltage levels. But I would expect a code for an APP as well.
Also graph the Oxygen sensors, they should respond very fast and go rich under wide open throttle and then lean when decel due to injector cut-off. Slow response could be an oxygen sensor heater fault. If they go lean under wide open throttle, then you could have a fuel pressure/volume problem. So, you can see these cars have a lot of different problems, some have one after another. Are there any other details you can give?

Never fully trust a scan tool test, it's only one part of the diagnosis. When it comes to the Purge valve on these, they can stick open if the charcoal canister fails, you shouldn't be able to blow any air through it one direction toward the intake manifold if it's not energized. But keep track of the direction the lines are on it before disconnecting. I have seen them stick open due to a small piece of a failed charcoal canister, check that the purge isn't stuck open by any amount. but there looks to be a fuel pressure port on the rail, here's the service info on it. Make sure it holds fuel pressure at key On as well, if there's a bad check valve in the fuel pump assembly it will drop off pressure quick, this is a return less system so if pressure drops off too fast I block off the fuel rail to see if it's the pump or injectors leaking down.

https://www.2carpros.com/articles/how-to-test-a-fuel-injector

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

Okay, try graphing just one oxygen sensor, if you're only looking at one data PID at a time, the scan tool will refresh the live data much faster. Are you getting a 0-1volt signal from the front Oxygen sensor in live data? Some info is showing this an Air/Fuel ratio sensor for the front oxygen sensor, which is what I would think on a 2010, but then theres some showing it a narrow band regular oxygen sensor up front. There are a bunch of different designs when it comes to this vehicle. Under the basic generic OBD2 live data it will most likely be a 0-1v signal, under the manufacturer side of a scan tool (so advanced data) it will show either a 0-1v signal or an A/F equivalence Ratio signal and works off current flow. But if you're seeing a high negative fuel trim number under wide open throttle, then checking the response of the oxygen sensor would be my next check, because a slow responding sensor can cause a lack of fuel, if the oxygen sensor heater is not working the sensor wont respond fast enough either. Sometimes I'll make a vacuum leak for a few seconds while monitoring the 02 and make sure it will go lean, and rich, since these little engines only have that sensor for feedback as to the air fuel ratio.

Okay, since you're dealing with something that is not within parameters of setting any codes, I think you should run through a VE test and see if the engine is breathing correctly, and that the MAF is sending a good signal, it may be under reporting air flow but not a point yet to where its setting a code. Especially if the MAF has been replaced with an aftermarket sensor in the past. This is a link to a VE calculator, the button at the top of the page will show the exact instructions for running the test, basically you're going to go to wide open throttle and record the highest RPM achieved, along with the MAF grams per second (g/s), intake air temp reading, engine size, and the Baro reading you can look up at the time of the test either on your local weather or some scan tools will give the barometric reading. Because you're going to be at wide open throttle, the baro and MAP should be reading the same. Wide open throttle will allow for atmospheric pressure to be equal to the intake manifold pressure, When you record scan tool data, you will want to scroll back through the live data until you get to the highest RPM reading and use the rest of the live data readings from that point as well. This test should also reveal a bad MAF reading if that's the case. The estimated Volumetric Efficiency (EST_VE) % will come up low if either the MAF is reporting incorrectly, or if there is a restricted exhaust due to bad Catalytic converter which can be backed up by a back pressure test at the front 02 location.

https://atgtraining.com/atg-volumetric-efficiency-calculator/

Okay, this peak RPM is good, I know doing this test the vehicle does seem like its screaming, that's why we record the live data and scroll back to that highest RPM to get our data, you can see it would be very difficult to get accurate data at that one point. I would be curious to see if the Calculated Load was close to the Theoretical Load.

Is this data from the manufacturer's side of the scan tool or global OBD2 scan data? If you're on the Chevy side I would try this test again under global OBD2 scan data, just to be sure you're not getting any substituted values in there and grab the Calculated Load and Long Term/Short Term Fuel trims as well. I'll say this is a difficult vehicle, without any obvious issues showing under up. No codes, 02 seems to be responding correctly. But the comment on the fuel trims under accel has me wondering about the MAF not reporting correctly or low fuel volume. I assuming the 02 is going lean as well under accel, possibly staying low voltage the entire time when it should be going rich.

I found a good video that will help with the VE test a bit more. but since this is just under some code setting criteria and making a call on expensive sensors or a cat without being sure can be costly. In the video he goes into the fuel trims more and what to watch for if the MAF is under reporting air flow, right around 6min in, he explains about the ECM and its fuel calculations. If the MAF is under reporting air flow going into higher RPMs you should see some correction in the fuel trim numbers due to the 02 feeding back a lean exhaust. That wouldn't really show up for a long term (learned value) so much because the vehicle is rarely at these high numbers.
I added the OEM wiring diagram for the MAF if you need to check its powers and ground.
I'm really curious to see what the fault is on this vehicle, it's a close call, but the fuel trims under acceleration is a clue here.
Being at almost 84% VE, I don't think it would be a cat, but if you want to double check that, you can do a back pressure test at the front 02 location. You shouldn't be over 1.5psi at idle, I use an old 02 threaded section with an adapter for my vacuum gauge, you don't need to keep it on there long, just long enough to get a reading. I have seen people melt their vacuum gauges with just leaving it on the exhaust. Most restricted exhausts will show a much higher number right away and its almost something you can hear on these smaller engines; with that sort of hiss they make when the exhaust is just pushing out any place it can. Let us know what you find.

https://www.youtube.com/watch?v=CfwTc7Im0dE&list=PLfPHKlLGXDPIVTQBWC0Lwq9P7SBm8vuH-&index=10

I wouldn't give up on it, you have a lot of information already, I understand how difficult things can be when working with limited scan tools and other testing gear, I've had to work through all the same situations as well. We can't all afford $5,000 scan tools. none of mine are that expensive. But keep it simple, you were able to see the fuel trims go positive under acceleration, correct? So that means the exhaust has to be lean, For now graph your rear 02, and give it some heavy throttle while monitoring the short term trims, if it goes positive more than +10-15% and the 02 goes to low voltage you know the ECM is compensating for a lean exhaust. So that kind of leaves you with fuel pressure or the MAF is under reporting air flow.

I don't think the cat is the issue either, if you mess with the VE numbers just a little, such as changing the MAF reading just to 50g/s increases the
est_ VE to 97.86%. With that said, you could run to AutoZone grab some MAF cleaner spray (follow the instructions on the can) and see if just cleaning the sensor makes a difference. It's good to have a can of MAF cleaner anyway. Check the MAF voltage and ground, use a test light across the two pins of the MAF connector, orange/black is B+ from a 10-Amp fuse, and the black wire is the Ground.

On these more modern vehicles, I see a slight amount of carbon build up around the edge of the throttle plates and throttle bore being cleaned with some carburetor clean on a rag make a hug difference, just from getting the air flow turbulence corrected. Don't spray the throttle plates directly, you don't want the cleaner getting into the TB motor. I've started to look closer at these little things and I am always surprised at how much better the engine runs after I'm done. But never give up, then the car wins and that's just not allowable. =)
Here's a few more guides that can help. I really want to see this thing fixed, it helps others with this same year/model in the future that might run into the same problem.

https://www.2carpros.com/articles/repair-lean-mixture-codes-p0171-or-p0174-on-some-manufacturers

https://www.2carpros.com/articles/mass-air-flow-service

https://www.2carpros.com/articles/engine-surges