Got curious and went looking... Here's a couple of interesting threads on the matter. 2nd link is referenced in the first thread. Also not discussed is, when by-passing or blocking the vacuum hose, one would need to do some coding so the ecu doesn't throw a fault code.
http://www.xoutpost.com/bmw-sav-foru...ass-valve.html
http://www.xoutpost.com/bmw-sav-foru...-when-hot.html