I have been experiencing a surging idle and I performed a smoke test to track down vacuum leaks. During the test I noticed smoke coming from the area where the bypass control diaphragm is. Best I can describe is the smoke looks like it’s coming from the spring area where that diaphragm hooks to the IAB plate for the vacuum secondaries (I think). I’ll post a picture for better description.

I added another photo of an actual IAB plate and circled the area I think the leak is coming from. It’s where the butterfly rod comes out of the plate and is controlled by the diaphragm.

Does anyone know of a gasket that is in place there? Or does the entire IAB plate need replaced? Thanks in advance!

 

Not an answer to your question, but I suggest that you also inspect the large rubber hose with the bellows that runs from the air filter to the throttle body. Ours tore at the bellows on the bottom and we didn't find out until it needed to be removed for other reasons. The car ran fine, even though it was sucking air (and some dirt) in through the gap in the rubber.