i was thinking about making my exhuast a bit louder, right now i have stock cat with a cherrybomb glasspack in place of the muffler....does anybody know how much louder it will get with a magnaflow hiigh flow cat an if ill expect a power loss or gain as well with mpg....my plenum is fixed an wasnt blown when i changed it so i dont think the stock one is clogged

 

High flow cat does make it quite a bit louder, and changes the tone a bit. Just changing the cat wont make any noticeable power difference imo. Get a better y-pipe with it.