whats better to have yet is some what quiet. a custom piping with a flowmaster or a bolt on?

 

bolt on.

you can find a bolt on kit that will produce both better numbers, and be reasonably quiet (they R & D the shit out of big name exhausts), depending on which one you get.

please also refer to this thread from last week:
https://www.tamparacing.com/forums/h...t-exhuast.html

 

depends on your cars setup?