I suspected its was a HELI governor but have played with them a bit and was wondering how you "tricked" it..

"Theoretical Idea Moment" - What if we built a "carb" with two throttle elements with and spray bar in between - No venturi per say . If we controlled both inlet and outlet with fixed curves and delays we should be able to control both the flow (speed) and the mixture profile.. Not an improvement on the solenoid in my opinion but a different method of control.