Hey guys I know you have had a gazillion people as this question but I am a retard and need it explained S-L-O-W-L-Y!! I just did a swap of a 02 Avalanche 5.3 into my 86 Silverado. A buddy of mine has HPTuners and he reflashed my ecm and removed VATS, emissions and down-stream O2s, we removed torque-management too. The problem that I am having is when we did it the truck ran great, I had the exhaust welded up and it was ok, when I got it home I romped on it really, really hard (I did a burn out half way up the block) after I did this it started running really crappy. The only codes that are triggered are P0300 random misfire, and it seems to only run bad in closed loop. Is it the tune? I have been fighting with it for a week and need some HELP!!!

THANKS GUYS!!!!

 

are you sure the car is in open loop mode?

 

Yes sir, at least that's what the code reader is saying.