how are your door locks working? If they also arent working(which i suspect) you could have a leak elsewhere. Your best bet is to buy a mitivac guage(about 30 bucks) and test each individual system of the car. E.G. Test the shutoff valve to see if it holds vacuum, if it does, then that isn't your problem. Test all diaphrams's/lines that you can find, you will eventually find your problem. It could even be a faulty trunk locking mechanism causing your engine to not shut off, these vacuum lines are a major PIA to fix, but are normally very inexpensive, just time consuming....
Ryan

__________________
83 300SD.......sold
96 integra SE....sold
99 a4 quattro....sold
2001 IS300.......sold
2002 330i.........current.
2004 highlander limited....current.