Dont worry about gas mileage, a turbo will give you the same gas mileage as a factory car. unless you beat on it, in which case it uses the hell out of fuel.. remember with a turbo isnt always on boost. If you are planning to run a turbo that is small as hell just got get to the 6psi range and dont care about future ugradability and power out put then a small cheap turbo will work, with such minimal lag you wont even know its there..