The tuner will help with the mileage, especially if you find someone that can do a custom tune once you get everything on the engine you plan on putting on it. I'm not sure if the newer Edge tuners will calibrate for the tire size or not on the 2000. I know the older ones wouldn't when I had mine. It's worth it to have the dealer re-calibrate the speedometer so the computer knows where the shift points really are supposed to be and can keep the engine in the happy range.
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