You can either get a bottle mounted gauge, or an in car gauge from autometer. I had an in car gauge...you will need to get a t-fitting and extra steel braided hose to go to the gauge though, so its a little on the expensive side. The good thing is you can monitor pressure from the drivers seat, and not have to open the trunk to do it.
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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