If he ran a 15.3 in that, he's not a good driver like you think he is. That is a time for a stock GSR to run, on street tires. In fact, I've seen faster on street tires, bone stock.
With i/h/e/headwork/slicks/gutted he should easily be into the 13's.
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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
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