just started my car up this morning, and it was popping and backfiring kinda bad. im just wondering what causes this or what should i check for? i noticed it slighty at idle, but if i would rev it-it would pop and backfire through the bullets. i left some big ol' black spots in the grass , but then i drove it real quick and it went away. doesnt pop or anything and revs real smooth at idle and at WOT. im still running the bolt-on's tune from pcm4less, i dont know if that makes a difference. also i drove my car open headers for a few days (sounds wicked) so i dont know if that contributed to the problem. as always thanks in advance for any help. i really need to get this damn car to the track so i can see what it can really do.