Having a issue with my 08 Sierra Denali and need a little help. Truck seems to stall/bogg at part throttle from 1st-2nd and barely pull through 1st gear almost holding from 4k-6k rpm at WOT as if all power was lost. 1st gear is the only issues. All other gear perform well at WOT/cruising like nothing is wrong. About 10 tanks of 93 has been ran through it and the issue still exists. Filter & MAF has been cleaned, computer reset and T/B clean to the best of my ability without taking the sensor apart. Any help would be appreciated. BTW, using a basic hand tool shows that the timing drops to -12 degrees when the truck stalls on the 1/2 throttle 1st gear pulls.

 

Sounds like torque reduction if it during the 1-2 shift but -12 seems a bit much

 

Same thing I said but Torque Management has been removed. Yea it'll spike -12 and come back up.

 

Do anyone else have a slight idea? Is it possibly a knock sensor.