I have a Budget Y and a Custom 2.5" cat-back with a Flowmaster 40 series muffler. At certain Rpms (2K,3.5K) it sounds really raspy, like metal clanking against each other. What could the problem be. The b-pipe is not mandrel bent.

 

Add a resonator into your bpipe and see how well that helps.

 

Yeah I just bought a budget b-pipe and a hi flow cat
I hope that does the trick

 

Yea you need a resonator, that was my problem. I had the same problem... it sounded like crap and would fart all over the place.