[JLMounce]

The regulator is easy to change. Two Allen head screws holding the backing plate. You can pull it out from there. It's o-ring sealed, so no gaskets to mess with.

If you run a vacuum line from the regulator to the back of the unit, check it for fuel. If it has liquid fuel in it, the diaphragm is shot.

In regards to not holding line pressure, that can be indicative of a problem, but not always. Not all fuel pumps have an internal check valve to hold pressure after the pump is off.

The easiest way to get a fuel pressure gauge on the system is to plumb it into one of the auxiliary fuel feed ports on the FiTech.