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      12-17-2012, 09:16 PM   #17
roadkillrob
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Drives: 08 335i,16 X5 35i,12 C63 AMG
Join Date: Jul 2007
Location: Boston

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It has nothing at all to do with emissions or it could not be legally disabled - PE exhaust would need to say for off road use only if disabling the flap messed up emissions and a non functional flapper would need to set the check engine light if it was part of the emissions requirements.

It is purely to pass the noise tests at certain RPM's that sound levels are measured at, then can open to allow more flow and better sound at higher RPM's.

Torque - no difference, that is controller by how quick boost is built and how high boost pressure is, that is controlled by the wastegates.
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2008 E93 335i, MHD, HPF IC, Injen Intake, AR DPs, Xhp TCU Flash
2016 X5 M-sport 35i JB Stage 1
2014 Mercedes C63 507 Edition