Can someone explain to me the ins and outs of the tuners available out there. A few things such as how they work, their positives, and their negatives. I don't have many mods, but I'd like the car work better with what I got. The reason I am considering a handheld tune instead of a "real" one, is because I have heard that with some tuners the tune can be changed to factory stock, if needing to go to Ford for warranty work. Any help is appreciated. 
