My roomate had them with a milled head and JDM itr pistons, and it was fine. But i also do know that with the stage 2 cams you can't separate them by I think 2 degrees, otherwise the valves will hit each other. As for the valves hitting the piston with a milled head
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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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