It does not introduce pressure pre-compressor as it a small amount of air. The volume of air does not matter, it's the pressure you're trying to maintain at the WG that does. If you're venting/sucking pressure away from the boost controllers, you're making the MBC useless.
With the way I described, you will NEVER overboost unless you pop a line off. The ultimate path of least resistance will use the EBCS unless it is closed off too much and then the MBC comes into play.