what is your idle speed, warm engine, and all accessories OFF?
if you are running 800 +/- 50rpm. and idle is smooth, you can almost rule out vacuum probs.(that is not set in stone... but it is a good base to start from)
If the above applies, then train your sights on the vacuum lines that come into play with open throttle
catch the drift?
... and there aren't many
*the beauty of BMW engines is they do not use a lot of vacuum as a measure for engine performance, unlike japanese and american cars. The EVAP vacuum lines of course are there because the law and "clean air" acts requires it... and unless the leak in that area is an obvious leak where u can audibly hear a *hissing noise, that will not be cause for stall.
for DIY... the brake or carb cleaner trick is prolly the best way to check for leak/s. a change in idle speed whle u are spraying will point to the leak. There are no vacuum lines anywhere near the alternator; so yes, training a stream of ANY type of liquid on a running altrernator is a downright foolish thing to do ;-)