Ford Performance will begin selling stage packages of parts and engine tunes called Power Packs for stock Mustang GTs; they work on cars from the 2015 to 2017 model years. Power Pack 1 is very basic featuring just a K&N high-flow air filter and an ECU tune, yielding gains of 13 horsepower and 16 lb-ft of torque. It also provides a nice low-end bump to torque with an extra 40 lb-ft at 1500 rpm.
The second two packages bring parts from the wild, track-oriented Shelby GT350. They each come with their own tuning calibrations and slightly differing parts groups. Power Pack 2 includes the GT350's cold-air intake and an 87-mm throttle body, while stage three adds the GT350's intake manifold. Stage two adds 21 hp and 24 lb-ft of torque; Power Pack 3 is good for 37 hp and 5 lb-ft of peak torque. The reason for the lower peak torque gain is because the GT350 intake manifold causes a shift in power and torque up the rev band. The benefit though is a very impressive top-end gain of 60 hp at 7500 rpm.
The first package goes on sale at the beginning of August with the other two becoming available in September and October. Of note for prospective buyers is that these packages are 50-state legal. So even Mustang GT owners in California and other CARB states can enjoy these new upgrades. That being said, the packages will only be available in North America for the time being.