[patrickt]

When you put the vacuum gauge on your engine (manifold vacuum, not ported from the carb) post the results. Specifically the behavior of the needle, not just the numbers. For instance, if the needle appears to be reasonably steady around a certain number but then dives down several inches, then back to where it was originally hovering again, and does so in a rhythmic pattern. I've been a believer in the vacuum gauge as an initial diagnostic tool for a long time. Once you have a tool that is indicating a problem you can then take more "non-invasive" diagnostic steps to see if you can make the gauge read normally, even for just a few seconds. That will help you pinpoint the problem.