I have a 97 1500 with the 5.9. I'm after towing a small car on a trailer I've noticed that my truck wont accelerate past 35 on flat land. It generally stays in 2nd but when it shifts into 3rd and i try to accelerate it drops down to 2nd and wont go past 2200 rpms, please help so I dont drop a bunch of money into new parts

 

 

checked the plenum; stock. Hear that if I take out the O2 sensor that will be a quick diagnosis, turns out that's it. Just a clogged cat. Now runs perfectly fine, just need to upgrade the plenum, and do something about the cat( run a pipe through)