[MA70-3.0GT]

That's half the problem with long running problems like this, you can end up running in circles if you forget what's been done. If something takes more than a few days to "nail" I like to start a sort of diary of what was tried, what readings of things were on a certain day, what happened when I did a certain thing/disconnected X sensor or Y plug & stuff like that... with any luck the computer will be able to get things straight anyhow, sounds like all the wiring should be OK... Hey here's a leftfield one, have you tried running it for a short time with the alternator unhooked (belt off not just unplugged)?

Like I say rather left of field and can only try this for one or two pulls from cold as the water pump would be down too, but I have heard of an electrically "noisy" alternator causing problems as it spun before...