Thanks a bunch. I will definitely try this before a teardown. I'll try my best to report what I find out after this weekend.

 

Well, I did the cleaning job today. I did not remove the head, but I did remove all the injectors and clean them and replace the EGR valve. After all is said and done, the truck runs much better (even though I have 87 octane in it now and I bumped the base timing back to ten degrees from seven). I used GM Top Engine Cleaner recommended by Silver Streak and it performed very much like Sea Foam (if you've never used these products, you're in for a treat in your neighborhood.

The injectors were very dirty. My friend who is a mechanic said he has never see injectors this dirty in a ten year-old vehicle. We cleaned them and replaced all the O rings. When I took one of the small directional nozzles from every can of parts cleaner you've ever bought and pushed it in one of the fuel injector holes in the manifold, it came out very black and full of sludge . Which tells me that my fight to clean this engine well still goes on. One day, I may try the cleaning system which attaches to the Schrader valve on the fuel rail.

Unfortunately, I also discovered that I am experiencing a small amount of blow-by. I did a compression test and all cylinders were well within accepted parameters and the spark plugs looked good. So at least it's not affecting the engine very much right now

 

After doing all the aforementioned work and observing it for a few days, the truck now pings just a bit when initially taking off in gears 1-3 (87 octane Amoco and ten degree timing). The injectors are very clean and the head and valves are getting cleaner thanks to GM Top Engine Cleaner.

Could this be an oil-related issue such as weak pump, clogged screen, bad valve seals, etc.? I'm also getting a little blow-by into my air filter. I have installed a brand new PCV valve and breather cap (and they seem to have good vacuum).