Just thinking out loud:
Less pressure going to the tank, fuel flows slower to the carb, leaner mixture, more fuel mileage. Also there when you get off throttle, there won't be a sudden surge of fuel going to the carb. I've read a test in a magazine before of the Drake running 1/10 truck without the pressure line going to the tank.
I think thats what the Orion CPD funtion is. It keeps the pressure constant throughout the entire throttle range. When you get off throttle the excess pressure goes into the rubber bladder and slowly bleeds back into the tank. When you get on throttle the rubber bladder opens up and dumps the pressure back into the tank faster.
Speedpassion : Speedpower : East Coast Bodies