I have had a turbo tweak chip in my car for a while now. The only problem I seem to be having is dreadful gas mileage, as in 147 miles to a tank. Is it normal to get bad mileage with Turbotweak chips? Now my fuel plugs look to be in pristine condition, so I think the tune is fine on that part. My car is mostly stock excluding the turbotweak chip. Any help would be appreciated.