+1 on sap. Check both the hose from the pump (for a hole and/or for squishiness) and check that the vac line is intact too.
Also, look in the valve to see if it's clogged from decomposed hose plugging it up. I had this issue...and it caused my car to stall on cold start.
I'm so depressed. No one wants to come see me in NYC: Sat, Oct. 8, 6 p.m. at Greenwich Village Comedy Club.
Mangofy your E46!