This is the GEN II BCS M135i Powervalve variable tone boost actuated stainless steel performance exhaust system. The video shows the comparison free revving between the BCS system with the Powervalve set to auto and the BCS system with the valve in the fully open position made possible by use of the actuator arm clamp mod.
Normally with the system being boost actuated the system would only be in the fully open position when the car is boosting and therefore renders the valve inactive whilst the static revving process is taking place.
Thanks for looking

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