With the vehicles of today, you don't change the chip, you buy a programmer. I don't have a Ford, but did buy a programmer for a GMC, an '07 5.3 liter, and couldn't really tell the difference. However, I was able to tell the difference when I changed the rear end gears from 3.73 to 4.10:1.
Quite a bit more towing power, and actually got a little better fuel mileage. I did need the programmer to calibrate the speedometer.
"To compel a man to subsidize with his taxes the propagation of ideas which he disbelieves and abhors is sinful and tyrannical."-- Thomas Jefferson