i still have no clue what it is, it is now backfiring when i drive it hard lkike around 4k with my foot to the floor, it just backfires and then itll backfire enough to give me a CEL and send it into limp mode and nail the rev limiter at 3500.. have no clue but it does sound like deatonation, what else could cause this stuff?

could it be a timing issue, could it have something to do with me running open header? what is it!!!!!!!

EDIT: the car actually did not do any of this until i unbolted my exhaust.....