Whoa man, just read all this!!.... Nothing worse than fixing someone else's shite! Although to be fair, some of it has been amusing!?!?! I liked the dash lights best I think!... WTFUNK??????lol
With regards your issue, I have been in similar positions before scratching my head trying loads of different things and honestly starting to believe it may be voodoo at play.... But it has nearly always been the basics - of course sometimes hidden via some voodoo shield...
Personally I would start again at the beginning;
Fuelling
- Check for dirt in lines again, so often if a vehicle hasn't run for a while and there was shit, there probably / possibly still is. You also mention an improvement after cleaning which after a period the problem returned.
- If this is an injection system start with fuel pressure - you can often fit an inline unit at least temporarily then see what it does, and then what its doing when running like a POS... I bought a really cheap kit of eBay to diagnose my Jimny ( happy to lend it you if needed)
- You can also do a test on the injector to see the spray pattern and how much it fires out per minute or a given time - someone should have figures perhaps for what is expected?.
Ignition
- I assume at this stage we don't know if the crank is timed to the cam properly? tbh if it was proper out I t would be much worse all the time... But just a thought.
- You could always try rotating the dizzy in small increments when the problem arises, that would at least tell if its just a timing issue.
- I also tend to carry tools when testing these things so I can also whip out the spark plugs individually and do the basic spark test...
- One point of note I think Scottie said, if you are missing connectors off what look like vac circuits I'd try figure that out or at least make sure they are blocked off..
I'm sure I'll be just telling you how to suck eggs here, so apologies! But I know how frustrating this shit can be...
And to be honest, looking at the wiring one would have expected the issue to lie there... Have you thought about just making / getting a new loom? A lot of these looms are probably tired anyway....
Goodluck man! So much stuff you've fixed already
