FMU Question

an fmu is a really crude way of tunning. Very simple any one can bolt it on. The problem with an fmu is that it increases fuel pressure x amount per x amount of boost. The more boost you push the less effective they are. Since your fuel system can only handle so much pressure before it just overwhelms the injectors. You will also get lean and rich spots through out the powerband. I would say that the fmu could be a factor in that 10mpg i would also make sure that your ignition system plugs, cap/rotor, wires are good to go. The way they have the fmu hooked up is ok. I hope i awnsered your questions and gave you a little more insight about fmu's.

The FMU should have no effect without boost being supplied to it.
I would keep a vacuum line to it so it stays wide open during higher vacuum conditions, and thus won't pinch the return. Like when the car is under light throttle, or idling.