i run the APN header, 2.5 inch exhaust pipe to my 2.5 in magnaflow high flow cat, then 2.5 to my flowmaster super 40 dumped before axle with a 3.5 in turn down. dont dump the exhaust unless you want alot of drone, it gives me a headache lol im going to fix it. apn header made it sound better and felt more improvement from the engine.