most definitly but i see alot of people who use SAFC or othe types of fuel piggy backs and they have relly rich air fuel ratios at WOT, and just becuase its WOT doesnt mean that gas mileage is going to be bad, there are big differences in having WOT numbers in the 10 and then having the numbers tuned in the high 11's or the optmum 12:1, most of the times i think people who use safc or cu piggy bakcs keep their air fuel ratios in a mor rich state beucse they are afraid of blowing up thier motor, butyou gotta get it on a dyno, tune the air fuel ratios with your or te shops wideband, and get those numbers in a decent ratio state.
its such a misconceptin that boost is bad on gas mileage, and its people who dont tune turbo engnes, or do poor tuning, or use poor programing or piggybacks that claim bad gas mileage then EVRYONE thinks oost is bad on gas.