I set my wastegate at the max psi i wanted and then set the boost valve 2 or so psi less. You can get a stronger spring or shim the one in it with small washers to get a higher psi if needed.
Assuming the wastegate actuator spring is strong enough to hold the puck closed against the backpressure, the Grainger Valve will be able to get you as much pressure as your turbo can possibly make.
