RPM Stability

[txlawless]

So this one is a little complicated

I drive a 2011 GMC sierra denali, it has the 6.2L V8 with long tube headers and cold air intake. It has also been tuned trying to fix the issue with no luck. 

While driving about 30-40 mph it begins to buck or lag like the truck is misfiring but there are no codes and i dont believe it is actually misfiring. it seems to struggle unless i am on the gas constantly. It has a similar issue when in the 50-60 mph range as well. Any other time the truck seems to run fine. The best way to describe the anomaly is it seems to oscillate almost for the time it does this instead of smooth acceleration or smooth cruising. It isnt the tac either, it can be heard in the exhaust that it is not running smooth. 

 

The things i have done chasing the problem: New injectors, new spark plugs, oil catch can, new spark plug wires, tune, replaced transfer case, cleaned throttle body, new throttle position sensor, new crank shaft position sensor, cleaned all grounds, new MAF, new MAP, new o2 sensors, new air intake manifold.

 

I am starting to think this truck will never be fixed. HELP WANTED lol 

Thank you for your time.  

[CamGTP]

Could be the torque converter.

 

If your tuner is smart enough or if you are the tuner, you can try disabling the torque converter within the tune to see if the problem goes away.

[txlawless]

So i actually replaced my catalytic converters today and it seems to have fixed the issue. If not, the torque converter is next.