On one of my 1998 454 MPI engines, when I hook up a fuel pressure gauge, I get a reading of about 30 PSI with the ignition switch on. Once I start the engine my pressure gauge goes all the way up 70 PSI and rapidly fluctuates between 70 and 80 PSI. When I shut off this engine the pressure goes back down to 30 PSI. Do I have a bad regulator?