I'm not too knowledgeable in this area. I've heard that a preformance programmer can help increase gas mileage, is this true?? If so does anyone know the best kind to get for that??

 

First read this, it's probably the best explanation for new users out there:
http://www.f150online.com/forums/chi...unes-read.html

If you're buying it simply for mileage gains you may be disappointed. Every truck responds differently to tuning, some see mileage gains some don't. Driving habits are the largest influence on fuel efficiency.