I spliced into the line from fuel filter to fuel rail inlet and Tee'd in a pressure gauge, and i get 48 psi with the FPR line connected, and 52 psi disconnected. It is a stock fuel regulator and the car runs and drives perfectly fine. Should i correct it or leave it alone?

The gauge i used was from a pneumatic air pressure regulator from my work, the regulator portion broke and they were going to throw it away, the gauge was functional so i figured it would be ok to use... Does it have to be a FUEL pressure gauge?