+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.
Upcoming comedy shows: March 3 at Broadway Comedy Club, NYC, 8 p.m. March 5, Tierney's Tavern, Montclair, NJ, 7:30 p.m. See Facebook for other shows and PM me if you can make one...love to see you there!
Mangofy your E46!