I did some experiments but not long enough to document the results yet.

What I found is running very low propane pressure, but also setting it to come on at very light throttle application does increase the MPG enough to I believe at this point come out in the black on the cost of the propane.

Downside is unless you have a second higher pressure setup to kick in at heavy throttle application you don't have the power increase wihtout stopping and resetting the reguator.

Two solenoid switches, two valves and two regulators would be the only way to have both. Probably need two arming switches as well, but I guess it could be set to both work together.