sure it does,depending on how much ya crank it up and how hard ya drive it. If you crank up the fuel the way to control it is to not mash the skinny pedal so hard. (I know, it's tough not to) If you drive it like ya might break the throttle pedal if ya push too hard you will see the mileage come back up. If ya want hi boost, some smoke and lots of power.......it takes fuel.Does tuning your P7100 effect your gas mileage? If so how much? How could I combat that?