I ran 3-1/2" Dynomax Race Bullets and they sounded like open headers. Tried the larger case welded (straight through) mufflers and I could still set off car alarms at idle. Sounded like a bunch of loud motorcycles. Finally git the 3" TTI exhaust with large Dynomax Turbo mufflers that come with the TTI kit. There seemed to be no change in performance, but now the car was much quieter.