I'm going to make a suggestion. Go to your local parts store and buy two cans of Berryman's B12 injector cleaner. In my experience it's the only one that works. I've tried Seafoam and Lucas with no results.
I'm told that what's happening with mine is the injectors have a glaze on the end facing the engine. When cold that glaze is hard and the fuel has to beat a hole in it before it will start. Sometimes it starts on 3, 4 or 5 cylinders. As it warms up, the others kick in one at a time and it runs fine. As long as I keep a supply of B12 in the fuel, the problem goes away. Sometimes, as in this past weekend, it was starting fine, then I topped off the tank and didn't put any in, and the problem resurfaced immediately.
Wednesday it wouldn't start. Fueled it up and put two cans in, it ran fine until Saturday when I refilled it and didn't put any in. Put more in yesterday and it's fine.
One day soon, when I can ride my motorcycle every day for a week or so, I'm going to remove the upper intake, remove the injectors and have them professionally cleaned. Until then, I bought a case of Berryman's from a gas station I am friendly with the owner. Costed $32.00 for 12 cans.
I'll report back when, or if, I have any news.
I've been using the stuff for years, sometimes two cans. Never caused a single problem with the fuel system. My sister told me she used regular with ethanol the entire 4 years she drove it, and had no problems. Perhaps the ethanol kept the problem at bay. In my experience, the truck pings badly on any fuel below 89 octane, so I don't use it. She probably didn't drive it as aggressively as I do though, so maybe it worked for her. Doesn't work for me. The Berryman's does.
Just try it and see what happens. It might work. If it does, you likely have the same problem with the injectors as I do.