Gutting your stock cat won't cause the CEL to come on unless you don't plug in the O2 sensor. I just ordered an OBD2 Carsound high flow cat for my 97 LS, so you do have options.
As for converting to OBD1, simply using an OBD1 ECU will not change the rev/speed limiters or the timing and fuel. You have to get an aftermarket ECU for that...and since you are turbo, that isn't for you. If you go OBD1, go Hondata.
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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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