Soak it with penetrating oil, it will wash out the threads.

Yes, it took a few times doing this. I had to force it pretty hard it spots, but it'* sealed up and running. The old filter was only a couple years old, but I can notice a much better flow just at the schraeder valve relieving pressure.

Anyway, voltage drops are still present after the new TB connector and cleaning. I noticed this also happens if I just coast a little ways it will start to drop. This is with RPMs around 1200, so I don't think it'* the alternator cutting out.

Does it make sense this is the missing ICM nut? I plan on replacing it of course, but I'm just curious if I should be looking into other things in the meantime. Isn't the ICM only used at start, or is there always current flowing through it? Is it even grounding through the bracket?

Replaced missing ICM nut. New plugs and wires. Voltage now sits under 14 V almost all the time after running for a few minutes. It is much worse with headlights on. It never seems to drop below 13-13.25 V no matter what. There is just a tiny bounce to the needle once it starts to drop, but for the most part it is very stable with slow fluctuations. What should I be looking at next?