Signs of a failing Fuel pressure Regulator?

Just noticing some issues and thought I would address the board to get some educated advice. As of late I have been noticing my fuel pressure will be at different pressures. Once it was 6psi another time at 7psi. The last race the gauge read 15psi at start up then went down to 9psi. I don't see it pushing fuel down the motor and the oil doesn't smell like gas but the plugs appear darkened. So what are the signs of a faulty fuel regulator?