Originally Posted by vetteman
Do you feel it's a booster problem when,as I mentioned, that the pedal fully returns when driving the vehicle with vac line unhooked from booster?
Yes, I believe it's a prob w/the booster. The valve I mentioned has a seat that has to hold vacuum, even a broken/weak internal valve spring has the potential to be the problem, but the booster would need to come apart to confirm this- something that's outside the ability of most guys, besides the poit that you shouldn't need to fix a problem not of your making.
Given the info you've provided and the checks you've made, if it's not
the booster, I'm at a loss.
It shouldn't cause the problem, but have you checked the vacuum check valve between the engine and the booster?