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      10-11-2012, 09:27 AM   #3
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Drives: 13 335i Sedan, 11 128i Cabrio
Join Date: Apr 2010
Location: Leland, NC

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The vacuum is there to operate the flap on the muffler to divert all exhaust to the passenger side muffler during warmup, primarily to reduce the sound. It also functions when cruising - step on the gas, the vacuum decreases and opens the flap. It won't hurt anything. Rather than unplugging the connector, get yourself a golf tee and plug the vacuum hose. This has been covered in other posts hundreds of times!

2013 F30 335i M-Sport 8AT/MPE/MPPK, 2011 128i M-sport Cabrio 6MT/PE
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