Bought my Excursion in July of this year. Since then I've added a exhaust system, 75 single shot injectors and a DP tuner. The problem I have now is I get 14 mpg at best (norm around13.8) with the econo setting. With the stock injectors and without exh I was getting 15. All mpg is hand calc. Now without chip I get 17 mpg pretty solid. I talked to dp and they responded with taking a bunch of fuel out of the programming in hopes of increasing my mpg (but also losing a bunch of hp). With the tuner the engine seems sluggish in the lower rpm. I've owned a psd before (99 f250) and was getting 19 mpg with superchip and a stock style k&n filter. Why is the truck responding better without the custom programmed chip. I have no codes nor have any problems otherwise. Something isn't right. Does any one have a similar issue or an idea of what the deal is? I have a lot of money in the chip with a custom program and I had to send the chip back (which I paid again) to have the shift points lowered. ( it wouldn't shift under 2500) your input is greatly appreciated . Thank you.