I would not expect significant changes in fuel consumption. Actual improvements will be in starting and drivability, especially on steep slopes and in hard bumps. Remember that the motor you will be putting this on is not new (even if rebuilt) and is not as efficient overall as new fuel injected vehicles of today. There is more to fuel efficiency than mere fuel metering, and while you will get more precise fuel metering from a good add-on fuel injection system, that's about all you will get. Fuel injection is definitely the way to go off road, but don't expect wild improvements in gas consumption.