We tested the sound level (decibels) of each muffler type using the Loudmouth tailpipes. Top to bottom: PowerFlo, Loudmouth II, and Loudmouth. The PowerFlo muffs were tested with the Loudmouth and the PowerFlo tail pipes. We tested a total of four different exhaust configurations. Each exhaust configuration was tested for interior decibels at idle and at a 50-70 mph blast using our trusty Radio Shack sound level meter. The exterior was tested at 30 feet and 3,000 rpm. Only the stock and the PowerFlo exhaust were tested while the Challenger made a pass going down the track.