Fueling & Injection - Fuel Pressure/Voltage Question

Is it possible that I’m loosing power at wide open throttle causing my fuel pressure to drop from 58 to 40 psi? I've had this problem for a while now and was wondering. If I'm cruising around the fuel pressure is steady, but one stomp on the peddle and the fuel pressure needle drops like a rock. I talked to one of the mechanics at work and he said that I might have to change the pulley on my alternator. Any help is greatly appreciated?

Is the pressure regulator good? With your mods do you know what the spec is supposed to be?

I still have the factory setup. I'm on my second bucket so I can assume that the intank regulator works since the other did the same thing. It should be at 60 psi I believe.