I know plenty of people that have passed with copper plugs, that's not the problem. Changing the type of spark plugs you run won't make you pass/fail the smog test. Are you running the stock header? Do you have any fuel system mods? What is your ignition timing at?
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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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