5.3L going into limp mode. Need Help!

[offrd]

It is a 2007 5.3 with a jims performance harness. After you initially crank it you can hit the throttle hard and it will roast a set of 42" iroks but after that it doesn't have any power. You can put it on the floor and it will hardly go. I have replaced the mass air, map, temp coolant sensors and has new o2 sensors. Any help would be greatly appreciated.

 

[muddinmetal]

It's the throttle body/ pedal position correlation in the drive by wire throttle system. 20% of the time it's the sensor in the pedal, 80% it needs a new throttle body

 

[wannabe]

dirty throttle body can also cause this

 

[InDaShop]

what code is in the ecm? P0121, maybe???

 

[TacomaJD]

Viagara usually fixes anything limp... :****: