You can't tell much by just taking the valve cover off and noticing it's clean. If the compression test checked out ok, then you should be good to go. As far as running on boost, as long as you are properly tuned and don't detonate, you whould be ok.
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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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