I had originally posted that I had a code P0190. This was not correct, but it was what I was told. I purchased my own scan tool and my 2005 Ford Escape Hybrid actually has 2 codes (P0191 and P1237).
At the same time codes appeared, I started getting an intermittent purge type sound and vibration from under the vehicle. It is most prominent near the fuel filter under the drivers side. Starts after vehicle is warmed up and gets worse and more frequent as time goes on. Happens when engine is on, car in park or in gear, car moving or not.

 

Not sure if all vehicles have a Schrader type fitting to check the fuel pressure but it might just be the fuel pressure regulator that supposed to dump excess fuel back to the tank.

 

Any chance someone out there knows what the pressure should be, and also what would cause the excess pressure?

 

Shop manual for an 08 says the fuel pressure should be 40psi when running. The fuel system doesn't have a return line; it just turns the pump on and off to maintain pressure. Your regulator might be bad or else the fuel pump or its driver circuit. When you first turn the car on but don't start the engine, the fuel pump should stop making noise after a few seconds. If it still makes noise then it isn't turning off like it should once the pressure comes up.