Cgramscobaltss/sc

I just recently got my car tuned but was having a problem before and it wasn't fixed after the tune. When monitoring throttle position while holding it steady it will drop to 0 for a second then jump back it makes the car buck like hell when taking off even at normal speeds I have an ls4 throttle body
Does anyone have any ideas or know a schematic of where the throttle body wires go into the pcm please help thanks