Here's the complete PowerFlo exhaust system with the four PowerFlo mufflers. It keeps interior resonance to a minimum-this way Sam and his wife can enjoy the tunes. All dyno and strip testing was performed with the stock and the PowerFlo system. SLP claims the PowerFlo system delivers only 2 horsepower less than their Loudmouth exhaust. The decibel numbers dropped to these levels. At 30 feet, 3,000 rpm: 82. Interior idle: 72. 50-70 mph: 88. The stock exhaust produced 83 decibels of sound going down the quarter-mile, while the PowerFlo showed us 88 going down-track.