06 GMC Yuk XL Denali. 220k miles, runs great except......every so often, when taking off from a stop, when i push down on the throttle pedal the truck will start to move, but then its as if the throttle linkage/wire was disconnected. The truck idles, doesnt bog or make any odd sounds from the engine. So i push the pedal down about 1/2" and keep it there, truck will start to move, then makes some gear or motor sound from low in the dash, the rpms drop to idle, the truck stops moving, i have to lift off the pedal, push back down and truck will start to move again. If i take off from stop and push the pedal down more than say 1", everything is fine all the time. Brought it to 4 shops and nobody can figure it out. Of course it doesnt do it when i take the mechanic for a ride. Shows no codes, disconnected neg cable for 5+mins to "reset" and didnt fix issue (i read to do that somewhere). Figure its the Throttle Position Sensor, so got new pedal, then got new throttle body, but issue still persists. One mechanic said that the pedal assembly is the pedal, a motor, and sensor, but I thought that is all 1 piece. Not sure where to look next.