I have a challenge for all master mechanics out there. My 5.7 Vortec starts sometimes and sometimes not. Now it won't at all. Here's what I know. Fuel pressure is 65psi KOEO and drops to 58 when starting. Pressure drops to 20psi in 10 seconds after turning off. I removed upper manifold, and fuel spider and reconnected the fuel lines and harness and turned key on. Exact results as above (including pressure drop to 20 psi)without a drop of fuel leaking from any injector, poppet, or regulator. Fuel pres regulator is 6 months old and pump is about 1-1/2 years old. Strong smell of fuel when trying to crank. I capped off the fuel supply line at the meter and turned on key. Pressure goes to 85 psi and then drops same as above. Removed one plug and have strong spark at the plug. Starting fluid does nothing. It has same symptoms as when the regulator went bad 6 months ago but everything under the manifold looked good. Only DTC codes are a cyl 4 misfire and a couple of O2 sensor codes that have been there forever. Only other clue is that when I turn the key back from start to "on" after trying to crank, the engine diesels for a second like it's trying to fire but can't quite get there. I can't figure out why it's flooding when nothing is leaking from the poppets. Any suggestions are appreciated.