LB7 trouble shooting.

[JeremyK]

i know there a lot of threads on this topic but haven't found one that matches mine exactly that also has a solution.
First time posting to this site. I recently bought an 02 Duramax (completely stock) and after getting it home it started to run like a dog. most of the time it takes excessive throttle to maintain highway speeds and just feels like a complete dog, and sometimes itll run just perfect. but even when its doggy if you floor it itll put you back in your seat its just doggy from light to mid throttle, and its not turbo lag. I drove up a fairly steep hill and today with no trailer and nothing in the bed and I was most of the way to the floor just to maintain 60. ive had it scanned and no codes except faulty wheel speed sensor. ive examined the intercooler tube on the drivers side and found no holes. the oil shows no sign of diesel. No smoke what so ever, maybe a slight puff when you first step on it. ive replaced the fuel filter, the air filter, cleaned the MAF, then swapped the MAF with another Duramax. The engine runs smooth and sound healthy. Ive considered weak cp3 but I think that would affect you more at wide open throttle rather than at mid throttle same with the turbo. i will be getting a rail pressure test done here in a few days im just wondering if there is another sensor that could be causing this, such as the MAP or the TPS or something like the FPRV. Any suggestions would be greatly appreciated.