Seems to me that the change in tank pressure, if we're talking about a controller based on tank pressure only, would have a fairly long time constant and wouldn't be able to keep up with the throttle changes the way the solenoid does, but a controller with both an air pump for fuel pressure and a solenoid valve might be an improvement over just a solenoid. Is it worth building a controller with mixture input to control the solenoid, rpm input to control the air pump, and throttle channel input to calculate an acceleration quantity of fuel to add?