Error code 0420?

So, I managed to find thinner plastic ones that managed to get under and be able to bend so that it could continue under despite the angle it was coming in at. I just had to pull it out a few times and rotate it to be able to depress all 4 prongs, because the slit in the tool was opened wider due to having to go around the bottom ridge, causing it to not depress one of the prongs. But I got it off and it did indeed have 2 ridges, I attached a picture. But I put it back on because I didn't want to proceed until I found the proper pressure specs I should be looking for on an 11 Frontier 4.0, I couldn't find anything on any 11 frontier, I tried looking in regular service manuals, but they didn't have that info, and I can't find any factory service manuals available. I know people are saying a generalized 40 at idle for most vehicles, some say 50, and then different pressures when running, but I want to know for sure. Do you know what pressures I should be looking for when idle/running/off for an 11 frontier and how fast it should take to build or lose pressure, and/or the procedure for checking the fuel pressure the 11 frontier.

Okay, so I tested it, at idle it's 47-48, after shutting it off after 15 minutes it's at 43-44, after 30 minutes it's at 37-38. Idk if the 47-48 is still within the normal idle range, and from what I've read if the pressure has gone down all the way within 15-30 minutes I probably have a leak, idk if that's just for a bad leak, and if mine is still going down faster than it should, or if that's about the normal rate it should go down. Also, I've been meaning to point out the symptoms I've been having in case it helps. It's been slightly sluggish accelerating, with a significant drop around 40mph when it's switching gears, which comes back up to the normal slightly sluggish around 45-50 MPH. Also, a very slight, barely noticeable, vibration at idle, that usually comes in waves. Lastly high rpms at startup, I think it's more intense when it has been sitting a while like overnight or a couple days, usually about 2,500 RPMs, sometimes 3,000 when it has been sitting longer, which quickly go down to 1,500ish within seconds, then gradually go back down to around 1,000 or slightly under withing a minute or 2. And I've read that high RPMs are normal if it's cold out, but I live in Florida so it's not cold out whatsoever, if anything it's hot. Idk if any of that helps.

So, up until now I've only been checking and noticing the p2a00 code come back after the check engine light comes back on after driving it for a couple days, but this time I decided to check randomly after like a day, before any check engine light lit up, and I got a P0420 code, which is said to be due to "catalyst system efficiency below threshold (Bank 1)" which is the side I just replaced the converter and upstream sensor on. After driving it another day or so that code disappeared and the p2a00 code reappeared along with the check engine light. I also got a p0603 code pretty much as soon as I cleared the codes I think, not sure if it was there before, apparently, it's due to PCM's Keep Alive Memory (KAM) self-test failing. But I think it's from me disconnecting the battery a few times when removing the fuel pump relay to release the fuel pressure before checking my fuel pressure a few times. That code also went away after driving it for like a day. So pretty sure/hoping that's all it was. So now I'm just wondering if the 02 sensor I installed shortly before replacing my converter is faulty. While driving I used a Bluetooth obdII scan tool to check out the voltage readings in comparison to the other banks 02 sensor and it's pretty erratic in comparison/ sometimes just way different, I attached some pics of the readings, the red lines are the problematic Bank 1 sensor, the green are bank 2. Can you tell just by those. Should I, or do you know how to, or is it possible to, test the 02 sensors pins with a multimeter to see if it's bad. Or do you have any other ideas what I should check before going down that avenue?

Sorry, I just noticed I was looking at the sensor 2(downstream) sensors, because how they had them labeled, I was expecting to be labeled like bank 1 sensor 1 and bank 2 sensor 1, with the bank displayed first but they had it has Sensor 1 bank 1 and sensor 1 bank 2, and I was reading fast and got it mixed up in my head. But the sensor 1's are actually really stable and even with each other, when Idle and when driving. But the sensor 2 readings are the ones that are very unstable. I couldn't remember which ones of the first ones I took where at idle so I took some more pics at idle and attached them, the first 4 are both the sensor 2's again, this time all at idle, after driving it around and letting them warm up a bit, the last 2 pics are of both the sensor 1's, in case you want to see those, I took them while driving because they were both just an identical flat line at idle, when driving there are only very marginal deviation from each other. But with the sensor 2's what's interesting is first how different they are, bank 1, the green line, the side with the error, stays relatively stable at little less than.05v, while bank 2, the red line, when stable, stays around.8v, way higher, the second interesting thing is that it's the bank 2 sensor that will occasionally drop drastically out of nowhere, just when idling, then shortly return back up to around.8v. So, I'm wondering if bank 2's maybe bad, and if that could cause back pressure to add pressure to bank 1's side or something to cause bank 1's sensor to be sensing a problem idk. The other thought is that since both sensor 1's are very stable and similar and it's the sensor 2's that are showing discrepancies, that seems to me like that might indicate an exhaust leak like you suggested, do you agree? I haven't gotten a chance to get in there and really check, a while ago when we first started looking into this, I just did a visual check and listened and felt for any exhaust coming out the catalyst joints/connection points, didn't get around to using soapy water to look for bubbles. But if that's the next likely suspect that will be the next thing I do. Also, I'm assuming if I can see the voltages of the sensors using the OBD scanner I shouldn't need to check the voltages of their data pins using a multimeter, correct?