Port & polish that GSR head, and put in ITR head internals and it will be faster than the ITR. And please explain why you think the bottom end has any affect on the flow rates of the head? I still think it's amazing how many people still think the b16 head flows SOOOOO much better than the GSR
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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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