1993 Chevy C1500 Pickup; 5.0L 2WD

This truck ran fine & then sat in storage for 4 years (it has 125K miles). Upon getting it out of storage I changed oil, coolant, air & fuel filter, drained fuel & filled w/ fresh 93 octane, replaced distributor, plugs & plug wires. I also had a new exhaust (Cat Conv & muffler) put on as the old one had holes in it and the truck was very loud.

Truck starts like a dream and idles/runs smoothly when I start it from cold. However, after it's warm & been run and then I shut it down, it doesn't want to start at all unless I floor the gas & hold it down until the engine fires and then works its way through a rough coughing & choking period of about 30-45 seconds. Then it's back to smooth idling and running until I shut it down again.

Could it be something with the EGR, O2 sensor or injectors in the TBI?