Is this normal?
I've found my fuel pressure (factory pump and regulator) vary with temperature. The pressure differential on a cold or cool engine will be from ~44 to 48 psig. With a hot engine (175 - 185°F) and underhood it is ~37 to 40 psig.

 

It's not temperature, it's engine vacuum (which can be affected by temperature, which affects engine speed and load) that controls the pressure. I don't see anything wrong with your pressure.

 

The pressures were measured at cold idle with Freescan reporting MAP readings of .33 to .34 and at hot idle with MAP readings of .32 to .33. My thought was the higher regulator temperature makes for lower spring tension in the unit allowing the intake pressure to cause higher return flow to the tank. Just wondering if all factory FPRs act like this.