Engine cranks but it can take up to 5 seconds to start.

I have done a complete tune up including spark plugs, wires, distributor cap, rotor button, & fuel filter. I changed the fuel pump, coil, and ignition control module. I also put in a starter in October. I hooked up a fuel pressure gauge & it reads 60 psi (normal is 60 - 66) for a split second, then it drops to 50 psi where it remains. Once it starts up, it runs with no problem & has never cut off but the initial start can take up to 5 seconds or more of cranking.