When I was doing Fords, I liked the Edge EZ. It wasn't a high powered box, only 50 HP, but it had better bottom end power than any of the programmers on the market. Good towing box, and it consistently netted me 1 - 1.5 mpg gains. Best of all, you just plugged it in under the hood, stuck the box on the fender-well, and forgot about it. The programmers would occasionally screw up, or guys would forget to reset to factory before taking them into a dealer. The dealer would reflash the computer and the guys would be out their money on the programmer.
Rod