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Message: <blockquote data-quote="shlim8" data-source="post: 610514" data-attributes="member: 25063">Yeah, if the exhaust has the valve at the tip, it's for connection to the vacuum pump/switch. I would suspect that if connect the valve, your low end torque should improve...But other than the slight loss of low end and more noise during idle, I don't see any harm in leaving it open... If you don't have the vacuum pump/switch in the boot on the passenger side, you'll need to get those retrofitted in order to automatically control the exhaust valve.Mine's currently permanently open as my darn exhaust valve is making a rattling sound at idle.... but mine's stock exhaust and it's a 335i. WIth a turbo engine, I don't notice any loss in low end torque, in fact, it should improve the low end (theoretically-faster spool up ?). Noise during idle is significantly louder though.</blockquote>