It will void at least part of the warranty, but it's a decent upgrade for a used car.
Ford would have you believe the Shelby GT is more than a dressed-up Mustang. For one thing, it's exclusive. Production is capped at about 6000 copies a year. And the Shelby name carries a lot of weight with Mustang enthusiasts. But if you want all the performance of the Shelby GT and don't need the stripes, various scoops, or Shelby name, you can save a lot of cash. All the upgrades on the Shelby GT are available from Ford Racing Performance Parts, and the parts come to $2656. Shipping and installation will cost extra, but it's still far cheaper than the Shelby GT. Unlike the Shelby, the do-it-yourself approach will void at least part of the factory warranty on a new Mustang GT, but it's a decent upgrade for a used car in need of some tweaks. Plus, you don't have to drive around with that silly fake hood scoop, which some might consider a bonus.