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 cranking. Pressure drops to 20psi in 120 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 to 20 psi in about 30 seconds. Removed #2 and #8 plug and have strong spark at both. Starting fluid does nothing. After attempting to start, plugs #2 and 8 were soaked. Clearly, I have a flooding problem, but can't figure out why. It has same symptoms as when the regulator went bad 6 months ago but everything under the manifold looked good except slight fuel wetness in rear half. 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. As a follow-up I went out during cold weather the other day and it cranked up like brand new. Let it sit a couple of days and no start again. Flooding and strong smell of fuel have accompanied every failed starting attempt. Any suggestions are appreciated.