Jim, I am hoping he'll tell me. When someone lists custom exhaust it makes me curious as dropping 4 cats is supposed to be worth 15hp, maybe somebody found some power in changing the resonator and muffler. I have wanted to try dropping the resonator and using a Borla Pro XS, best muffler IMHO, with an X-pipe addeD also. Just would need to find cat delete downpipeS less than $800.!!!