I suppose it's possible for a really big injector to be rated at a higher fuel pressure, but the 24# injectors we usually use are rated at 39psi. Anything near or over that will give you the 24# capacity or more.
Running it on a dyno with a wide band oxygen sensor will probably be the only sure way to confirm that you are getting enough fuel at your peak power.
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351W 89 Mustang GT Convertible