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      01-29-2013, 10:48 PM   #4
Sindarin
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Drives: BMW
Join Date: Jul 2012
Location: USA

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This?

http://www.1addicts.com/forums/showthread.php?t=796343

I've run into this on a E90 335i with N55. The damn vacuum line to the exhaust valve vacuum actuator is corrugated. If there is a leak (vacuum actuator defective or line is disconnected from actuator without plugging) it creates a high pitched whistle/beep noise. Note this vacuum line runs through the interior on its way back to the left rear of the vehicle causing the noise inside of the car.