Simply unplug the fuel relay and use the gasoline vapor directly into the air inlet of the intake. Use both the vacuum created as well as the transducer in the gasoline source to help vaporize the gasoline. This whole concept is very technical so be careful.
Feel free to register a vehicle here on fuelly with one of these devices and we will all be able to see how it compares to a normal vehicle of the same make and model.
Simply using tried and tested driving techniques can yeild 10-15% improvements in MPG. You can look at the vehicles that I have registered and tracked fuel usage with to see the potential.