Geez mate, have some patience, you only posted the question at 7.23pm on a Friday night!
Anyway the stock BOV can vary a bit in terms of how much pressure it'll hold, it'll probably start to bleed boost over 10psi but some can go higher. There's a trick where you can bend in the top of the BOV (to preload the spring) which will help it hold more boost, I did that on my old car and it worked fine at well over 16psi. It may have bled a bit but it seemed to do the job fairly well for a part that's meant to hold 7psi.
Either way though I don't think a blocked BOV should cause your car to stall all the time, I'd be wondering if they've left something open to the atmosphere or whether you might have some other problem. Try to unblock the BOV and take it for a drive to see if your stalling issue goes away. If it does, look for leaks - if you disconnect the return line and don't block it you'll have stalling issues for example. You can also try resetting the ECU, instructions for that are elsewhere on this site.