Intermittent stalling

Over the last few days, when I go to work in the morning, the truck starts and runs fine all the way to work. I get there and it sits for a couple of hours. When I go to start it again to start my route, I have had to pump the gas to get it to start and then keep feathering it for a couple of minutes before it would hold idle. Today, in the middle of my route, I stopped to deliver a package, shut it off while delivering the package, and took a few minutes to reorganize for the second half of my route. It did it again. Hard to get to start and had to idle it a minute before I could go.

No engine light and not shaking or skipping at all. The truck runs like a champ. Has brand new Delco plugs and wires (the ones the GM calls for), and newish distributor, distributor cap, and rotor. I have removed the thermostat for the summer months, as I have been doing for the last few years.

I have not had time to dig in yet, but my thoughts are (1) PCV valve (have not replaced it in the 40,000 miles that I have had it that I can remember) or (2) vacuum line leak. Is there anything else that I should check for? I plan on checking tomorrow afternoon.

I did check the PCV a few weeks ago when I was doing other things and it rattled like "I think" it is supposed to.