i had dual exit pipes after the muffler, which is currently rusting to hell. so far i've lost one pipe to rust, and the other side is on its way out. when if completely craps out i'm goin back to a single swept design. either put the stock back on, or a new stainless steel system. as far as power gains i didn't notice any and doubt there was. i had a 40 series as part of the system which it only made it sound sound different than stock