My 4-1 header has a CARB plate welded onto one of the runners. Certain headers are NOT carb approved...like the OEM JDM 4-1, DC JDM 4-1 etc...but there are 4-1 CARB approved headers.
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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