I recently had the greddy evo2 exhaust installed along with some helix test pipes. At WOT, I've been getting some strange sounds from the exhaust area. At first it sounded like mild backfiring, but not it feels like the whole exhaust system is either hitting against some real hard or backfiring like crazy. It only happens when I go WOT, then let off and let the revs die down. Any ideas as to what it could be? Maybe a leak? Broken gasket?

 

anyone?

 

Are you sure its not hitting/vibrating against anything? I had an issue with my piping hitting against the brace in the middle of the car. I have Stillen Exhaust. I also know some who had the same issue as me with Greddy Exhaust.