Got my new exhaust on a couple days ago (Mufflex Y-pipe, Hooker Cat back) and the car sounds AWESOME and everything its just that when leaving from a stop it feels like the y-pipe is hitting somewhere. it smoothes out at around 2k rpm. any way to fix this? I'm sure the banging pipes are causing false knock as well. i can feel it in the pedal and in the floorboard...

 

I have the same problem.

 

where is yours hitting?

 

Driver's side.