My friend had a custom exhaust built and he didn't put a resonator on (no it's not hella loud) It does drone at times after the freeway... So here's my question, If he added a resonator like flowmaster or something like that, does it restrict horsepower in any way or is the only function to silence the exhaust system. He has the 1st gen Cattman (made for SC, the one that whistles) so at times it can be a little louder than normal, but under normal throttle it seems tolerble. His greddy "muffler" needs replacement so I know that adds to the annoying noise.
Suggestions??