i have an 07.5 Chevy 1500 with the 5.3. i was getting P0121 codes which was for a throttle pedal position sensor. i replaced the pedal and the sensor but the code kept returning. so i googled some stuff and found my throttle body could need cleaned. so i took and cleaned it not moving the flapper at all. once i cleaned it, it had to relearn( i went through all the steps for it to do so), it seemed to have relearned fine until the truck warms up. once the truck warms up and you take it out of drive the idle goes to about 2500 rpm. but when it is gear it goes down to 500-700 rpm. also when warm it seems that at about 10 mph the truck tries to give itself gas and accelerate to fight me breaking for a brief moment.

any ideas on how to fix this issue?

ps- i do have a bullydog tuner and have not had any codes since the 75 miles of driving even with the idle issues.

 

i had a similar issue, if it is possible try to get your pcm flashed back to stock, apparently mine was corrupted some how, after reflash the idle was fine.