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      07-28-2011, 05:59 PM   #19
Second Lieutenant

Drives: E60 M5
Join Date: Jun 2010
Location: USA

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Originally Posted by prodigymb View Post
thanks - i was actually talking to AJ about this earlier today. boost gauge is tapped right next to the bypass valve. so i will replace this line and see what happens. thanks for your input!!
Replace the vacuum line and do not T anything off the line to the BPV. If you have a leak somewhere in your boost gauge setup the BPV will not function correctly. Leave the BPV on a dedicated vacuum circuit for the dynotest.

If you have ruled out any obvious pressure leaks then most likely the BPV opens under boost because it does not have a 1:1 pressure valve/diaphragm.