Well, dang. Truck was problem free for 4 weeks. Today that ended. The engine started to stumble again so I pulled in to a parking lot, and there it died. I opened the hood and looked. I turned the key but didn't start the engine, I could hear that arching again, and the needle on the tack was jumping up and down. I jumped up on the truck and got in to the rear left side of the engine, where the sound is coming from. I stuck my hand in there to see if I could feel anything. It seemed to be an injector, but I can't say for sure.

The engine would not start, would crank but not fire. I was able to check for spark and I had spark. I noticed I could smell raw gas. I have already change everything on the ignition system. I checked for fuel pressure and I had it. It almost seems one, some, or possibly all the injectors were pulsing. Has me thinking a lot of gas got pumped in to the engine and flooded it. After a while I was able to get it started again and get home.

So, what could cause the injector(s) to pulse and cause the tach needle to jump?

PCM, or intermittent 12V (switched, or non-switched) going to PCM. Check wiring, fuses/sockets, and switched 12V relay for PCM.

I'm grasping at straws, as you can tell.

You and me both. I'm starting to think a bad PCM, or perhaps a bad injector that is locking on and flooding.