96 ram van 3.9L Lack of power

I have a problem with the van losing power after warming up.
I will run good for about 5-10 mins. and then it starts to backfire and lose power.
I hooked up a gauge to the fuel rail and I am getting 50psi when it runs ok, and the pressure drops to 19psi when I lose power.
Is this a bad fuel pump or is there a pressure regulator that may be causing the problem?

There is no regulator, it's the pump.