ASSume you have the spring/ball type valve?
as S'eagle said, just put it in line between wastegate and turbo and when you reach the point that overcomes the valve, boost will be applied to the wastegate (lose the solenoid and y-hose)
adjust your wastegate arm fairly loose, and test to see where your boost goes....if you get a spike at first, the valve is holding more boost than the wastegate...either tighten the wastegate or loosen the Grainger
this ASSumes you do not have a bleeder type valve that holds boost at a certain level
I have the Dawes and use it for quick spoolup....the wastegate still controls ultimate boost (once the Dawes opens)