96 Deville, hard start.

Im working on a 96 Deville with a 4.6. Its hard to start the first time you try to start it, meaning the engine spins over several times before it cranks. After its running, it runs fine. No missing, no problems, no codes. Nothing. Its just hard to start the first time, if you let it sit 30 mins after it cranks the first time, it will do the same thing again, almost like the fuel pressure is leaking down. Fuel pump, Fuel filter, plugs, wires, fuel pressure regulator, air filter, map sensor have all been changed. blah, Im lost. fuel pressure is about 50 lbs .