www.agency-power.com - The Agency Power Electronic Valve Controlled Exhaust for the BMW E63 M6 features the ability to change from a High Performance exhaust sound and power level to a more tame quiet exhaust level with the push of a button. The system used for this video is the header back variation that produced 46whp and 21 ft. lbs tq on the Vivid Racing Mustang II Dyno with the valves open. The exhaust system is a bolt on application with no changes to the ECU or other modifications needed.