How did you measure your mpg, from the dashboard? Remember, the dashboard only knows what the ECU is telling it, and is unaware of the changes the power commander is making. If you note your fuel quantity when refilling and the mileage since the last refill, you can calculate the true mpg. The results may not be so wonderful; I was fooled by this for a while too, until I thought it through.
Notwithstanding my comments, I agree the GT-Rx fueling package is very impressive.
I will measure it the old fashioned way as well. I had my suspicions also.
But, the overall results are tremendous.