Originally Posted by VetteMed

That was a thought of mine -- it acts like an old carbureted car with a small intake manifold gasket leak or carb gasket leak... I suppose I need to pull the plenum again.

I didn't use any sealant on the plenum gaskets when I reassembled (I was under the impression that none was needed). Hope that was correct.

Thanks for the info re: the passenger side vacuum line.