A word to the wise about looking for vacuum leaks by spraying anything at potential problem areas. The propellant in the spray can will find it's way into the air intake and cause a momentary change in idle speed/quality! Don't ask me how I know this!!! You can waste a lot of time chasing ghosts unless you eliminate this possibility. I've used a rolled up piece of cardboard to act as a snorkel over the air intake. Depending on what engine you're dealing with this takes a bit of imagination, but it's worth the effort.