One thing to note is that if you are doing a 4 banger (like a Go Devil engine) there will be a NORMAL 1-2 inch 'bounce'.. for any 4 banger. With only 4 intake valves there is a significant 'dead zone' between intakes opening.
Most of the vacuum videos/sites seem to center on 6-8cyl engines. If you have have a 4 cyl you *will* get a rapid, steady bounce only at idle.
