questions before going W/I

[max_torque]

To limit a superchargers boost you need a pre-charger throttle or restrictor, you could use a small electronic throttle body that is powered fully open by the "safe" signal from the water injection system, but when you have insufficient water flow it would be non powered, and the std return spring would close it. You would simple need to open the minimum throttle stop to hold the plate open sufficiently to provide some airflow, but not enough to build to "dangerous" levels of boost. Most current engine will have a Bosch or Siemems DC motor throttle body that would be suitable for this.