Low Fuel Pressure - electric fuel pump

I've got a potential issue with my fuel pressure. At the guage mounted inline with the fuel line to the carb, the pressure is reading 1.5 psi. The engine just quits while sitting at a red line but not all the time. However, it goes down the road just fine. We originally set the fuel pressure at 6-6.5 psi and it never quit at red lights. I don't know how it is now only getting 1.5 psi since we have not done any modifications or adjustments to the fuel system. The car is running an electric fuel pump and then goes into a Summit Racing fuel regulator then thru a fuel filter and then to the carb (750 Holley Double Pumper). The engine is a Magmun Performance crate 360. To make matters more wierd, we tried adjusting the fuel pressure at the regulator by turning the adjustment screw out but nothing happened. We even tried turning the screw in all the way to reduce the fuel pressure to zero (0) but it never changed from the 1.5 psi reading on the guage.

I'm wondering if there is something in the fuel pump that is keeping it from openin more or closing?

Thoughts???