I wouldn't be teeing the wastegate line off the BOV line, if you are using a "bleed-type" MBC. When the MBC is bleeding off pressure before it opens, it also bleeds off pressure to the top of the BOV, allowing it to leak slightly. If you are going to use the manifold as your wastegate pressure source with a bleedtype MBC, then use a seperate line directly from the manifold. The spring pressure type MBC should be okay, though.