I drive a 98 K2500 with 5.7. They don't have accessible injectors unless the upper intake is removed. Those distributor caps are problematic. I will only use a genuine GM Delco or a cap from Autozone. They both are made by Weil and will last better than some of the aftermarket caps. Some people put injector cleaner in every tank. I only use it if I think the gas is questionable. As others have stated, the compression test will let you know if there is a mechanical issue. If that is bad, the other stuff mentioned will not help.

What puzzles me is, it was sitting there idling and just started missing out of the blue.. Something electrical me thinks.

Gary my old yard truck here is a 98 k1500 and the same happened to me. I had replaced the cap, it soon went bad and I went to a better one and problem solved. Hence I mentioned cap earlier. Either way I think you are correct on the electrical direction.
Good luck.

Osky

The cap was replaced in Wyoming about 4 yrs ago.. looks good by sight but most likely a cheap one. I will replace that and rotor tomorrow.

Could be lit things, I have Colorado with inline 4 cyl, do u have dohc? I do, they have had trouble with them before , timing chain an gears

No, this is an old 305 V8. Still pretty standard engine other than fuel injection and electronic ignition.

Could be many things in reality. That's why I always screw in my compression tester when I pull out a fouled plug. It takes an extra minute, but saves us parts and time later. I figured you already had a scanner on it so that might tell you if an injector is causing it, or something else like an o2 sensor.

Started my 08 and left running for a couple hours check engine light came on. Misfire #7 cyl . After replacing plugs wires and good fuel still had same problem. It ended up being the coil.

Well, turned out it was the distributor cap!! Thanks for the suggestions. Found a cap and rotor on Amazon for $34 so I figured, heck my local NAPA can't be much worse. $81 later I installed it and it purrs like a kitten.

It is amazing what a little PM will do. If cap was done chances are so are the rotor, plugs, wires etc How long since last tune-up?

Hate to say I told you so......
Next time use Rockauto for parts, great parts good price.

Osky

4 yrs since tuneup.
Never heard of Rockauto. If I knew ahead of time, I would use Amazon. But here where I'm at, it's 120 miles to the nearest Walmart! To use a local business, which is good, but it costs thru the nose.