Don't know about the XS MBC, but Hallman, not possible. The reason for this is simple:
--Isnside Hallman you have a spring and a ball/facing the feeding nipple-from comp. cover/ and then another nipple/90* off the inlet one. As soos as the air overcomes the spring pressure it's going out to the WG... That is it.
--There are several things to look for, assuming that your WG is 100% working:
- Both nipples are threaded into the body of MBC. They have on O-ring at the end. It is however possible, that inlet and or outlet nipples got a little loose and you have a minor leak there, but this will cause overboosting you basically bleeding more pressure , before it reaches the WG therefore increasing PSI at which the WG opens.,
I had a case in which my Hallman/in-cockpit/, got one side a little loose/where the cable was attached and I was doing 28 PSI on pump and certainly I wasn't happy...
-- Second, there is a bleeder hole on the nipple to the WG- it should be there. If someone put another nipple with no hole, or the hole is closed for some reason, that will cause over boosting, because between shifts the excess air bleeds form there and if this isnot happening you'll be hitting huge spikes in boost......