Originally Posted by prodigymb
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.