[bimmerque]

Originally Posted by Chesmu

this may help.....from another thread...
"It is a common free mod to disconnect the hose. I did it to may e46 330 and will do it when I get my e90. The flap stays closed at lower RPM's. When you deactivate it, the sound is deeper/louder at idle and low speeds. It opens at higher RPM's to reduce backpressure so power is not reduced. The vehicle electronics don't know if it is connected or not.

Just make sure not to create a vacuum leak -- so seal up the hose end tightly by (typically) using a golf tee with a tie-strap tight around the end of the hose, then maybe even a wrap of tape over that. Strap the end of the hose up out of the way and you're all set to go.

Aftermarket exhausts are trying to give a better sound at all RPM's (and don't have to meet government imposed sound regulation), so there is no reason for them to add a valve that lowers the sound level and increases power robbing backpressure."

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