Whoa!! I have no clue as to why your mpg are worse. I'm not real savvy with tuners either, which is why I went to Lew for suggestions. I was very skeptical before buying a tuner. I was asking Diablo about their return policy before even purchasing a tuner. I cant say enough good things about my inTune. The most significant improvement has been the performance at highway speeds. Ever since I put on slightly taller tires, my ability to pass at +70 mph was terrible! The inTune gave me a much needed boost to accel to 85 mph in no time. On my 90mi drive home today, I noticed it very rarely downshifted on inclines. Before inTune, it would downshift two gears and hit 5000rpm to maintain highway speed up an incline. I performed data logging on my drive home this evening and just sent my logs to Lew.