Bring everybody up-to-date, I found it had the wrong spark plugs. Some ACDelco's with a 3/4 inch reach.
I looked at the heads to make sure they were SBC, cause I don't remember SBC using anything but 3/8 inch length. So, some new Autolites went in. What a pain in the behind to change. I can see I'll be cutting an access hole in the wheelhousing for number 8 plug.
I went and applied ECM diagnostic mode with the IAC out of car. I didn't have an assistant, so I lost the pintle and spring. Found the pintle, spring must be somewhere in NC, I never found it. I bought a new one from Advance Auto. Installed same and now I'm able to back off the 'curb idle' setting of the throttle plates.
Advanced base timing a couple degrees, sounds alittle better.
All in all it does run better, but, I think I have a faulty injector. When the engine is really hot, 200*F, it has a miss. I unplug this one injector, and no change from rpm. I swap injector harness with the next cylinder, and no change, ie, #4 harness onto #2 injector, #2 still works. Swap back to original set-up, #2 w/h on #2 inj, #4 w/h on #4 inj, #4 cyl is dead. I am running a can of Techron cleaner thru the tank.
I did this because the Mitchell CD repair schematic shows the odd number injectors are powered from one source of ECM, and even injectors are powered from another ECM source, batch fire(?) if you will. All even inj's get fired once and all odd inj's get fired separately, regardless what cylinder is where.
There ya go.....