Yep, almost any MBC will work in controlling boost spiking. Problems with MBC is that it will allow the boost to max out even at partial throttle. Not good. With the Unichip set up running with the supplied blue restrictor tubing, the boost don't max out unless you are hard on the gas pedal. If I were to go with the MBC, I'd rather go with the needle valve mod. For reasons that it is easier to tune and cheaper to obtain.
WRX-U, what does the dyno plot say on what type of mod set-up?