I have been having a problem with the truck for some time and I have put a lot of different repairs into the problem. The truck bucks and backfires at 1300-1500 RPM. When the you get to speed and stay constant over 60 slight throttle causes massive bucking and backfiring. I have changed TPS, IAC, Torque Converter Clutch Solenoid, Tranny Filter, Oxygen Sensor and now the cat. When one thing was done the problem would go away until the truck warmed up. The bucking was almost gone after the oxygen sensor was replaced but quickly returned after changing the cat. Any suggestions?

 

Plenum gasket.

http://www.hughesengines.com/Index/p...p?partid=27091

 

Any codes?

 

And, have checked your spark plugs (because of this)?