The limiter is lower because the CEL is on. For certain codes the CEL throws, the ECU puts the car into limp mode, scaling back on timing and lowering rev limiter, so you don't cause damage. Check the code.
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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