Loss of power

I can't even remember how it was done but when you change a lot of sensors the check engine light comes on and says code not learned, that was set a while back, exact number for pressure I don't know but the only original parts are the 6 injectors in the entire fuel system, even the tank straps, gas cap and filler neck are new. Car had same problem with the old stuff, nothing changed when everything was replaced for the fuel system, one shop said throttle position sensor so I put in a new AC Delco sensor, another shop said MAF so that was changed with an AC Delco. All of the other sensors were done with name brand parts, nothing generic.
I had one shop tell me it was pinging when you first hit the gas because of knock sensors, sensors were changed and it turned out to be a stretched timing chain. If I go to about 1/4 throttle it picks up speed pretty quick, you can feel the pull, I hit it and catch passing gear and it takes off, only at half way, that's it.
The injectors were cleaned and they seem to be functioning ok.

I pasted something below about the relearn. The CAT is a brand new magnaflow direct fit, it doesn't feel like a clogged or bad CAT.
The injectors were cleaned with 3 different brand fuel system cleaners for 3 tankfuls of gas and there was no change.
The injectors are $267 for 6 of them, they have 142000 miles on them. I am thinking that if the CAT was clogged or the injectors had issues why does it have power past the halfway point? I can go up a steep hill at 70MPH with throttle past halfway, if I let up and go to half it will die out until I go less or more.
Nothing on the 3800 series 2 is ever easy.

NOTE: If the crank sensor is bad and needs to be replaced, a special relearn procedure must be performed after the new sensor has been installed using a GM scan tool or an aftermarket scan tool with similar software. This step is necessary so the engine computer can correctly recognize the sensor's signals.

Not sure how it matters with car acting the same even with brand new fuel components minus the injectors but 38PSI is the average so the pressure is there, is it getting through the injectors or how could all 6 be bad at the same time is another question. I can go out right now and at 1/4 or a tiny bit more throttle feel great pickup and have no problem with a hill. You don't hear it bog down like lack of fuel you just feel the engine stop pulling and go quiet at halfway and start going again 3/4 or more.

P.S. I said code relearn, bad wording on my part it was case relearn.

38PSI