Droping pressure on the supercharger

You would need to find a large solenoid or butterfly valve to use as a bypass/recirculation valve. For fine tuning the max boost use an orifice/restricto to tune max boost pressures. You may have to use an isolation relay if the solenoid/actuator draws a good deal of power.

If you have a bypass valve in the system already you could force the unit partially open but then you may be looking at a mechanical system that could get more involved.

Either of these ways can work as well as some others, if either of these interest you or this sparks another idea let us know and we can try to provide more info.