Originally Posted by Fabrik8

A vac gauge should work, it's tough to tell if it would be to respond fast enough to register any abrupt changes when you went over a bump, etc. I would be surprised if that is the problem though, this is probably something bigger that can really make a hiccup. I'm talking a loose hose coupler or something like that. Anyway there are a lot of things that it could be, and an OBD2 scanner could tell some things if you can replicate the problem with the scanner attached. You might be able to see a sudden change in pressure, etc., that could point you to some possible causes.