I tested a 2 barrel holley projection kit on my sbc 350 that had a decent summit cam and the other aftermarket goodies. The thing was a complete pain in the a** from the start, ran rich, and wouldn't tune well with the analog computer.

It had excellent torque response, but even while tuning it, it would stay rich. I think the biggest issue was it was an open circuit EFI and not a closed circuit with all the sensors and what not.

MPG didn't seem to change at all. If anything I swapped back to my edelbrock carb cause the EFI was putting my MPG into the ground.