The best shift is one where you shift at peak hp, and the needle lands at peak torque in the next gear. A dyno will tell you...or you can look at dynos of stock/bolt on'd GSR's to get an idea.
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2015 Ford Mustang GT Fastback - Ingot Silver - 6M - Performance Package - Gibson Catback, JLT CAI, FR 47lb injectors, BAMA E85 tune, Eibach Sportline, BMR wheel hop kit, UPR oil separator, Steeda shifter bushing/bracket
Team B.O.B.® - Ballaz on a Budget