Poor man's ITR....
The si tranny probably has slightly shorter gearing with the same FD as the GSR. There probably wouldn't be much of a difference, but I would experiment with both, and see which one you like better, especially with boost.
The SI tranny is much quicker acceleration than the GSR. My roomate had a GSR hybrid civic, and switched from the GSR to the SI tranny, and it was night and day.
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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
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


