http://wwwrsphysse.anu.edu.au/~amh110/Tech...w_off_valve.htm
this link will help~~ it's info is accurate...the spring in your BOV is probably too soft which opens up too readily under the slightest pressure.
Vacuum from the plenum "sucks" the spring up opening the valve if your spring is too soft a lot of air is vented hence the stalling.
The AFM reads off a certain amount of air going into the engine and inject the specific quantity of fuel. However when the BOV vents off too much air there won't be enough air for combustion. that's when it stalls.
Depending on your BOV model, there's should be some sort of "dial" to adjust the spring...otherwise get a new spring? or BOV?
while it is true that BOV is usually better used in MAP system since MAP sensor sits after the BOV, if adjusted correctly (does not vents too much air) it should also be able to be used in AFM system.