1991 245. Free to me but has some issues to be sorted out before I can get it past safety inspection.

Lately, I've been focused on a number of the larger and more pressing issues, but I have noticed that my tailgate wiring is flakely and I've just about arrived at that point in the repair process.

Symptoms
The cyclops brake light is intermittent, rear wiper does not work, the rear power lock rarely actuates, and the license plate lights do not work at all. My educated guess is that the small wiring harness that passes the tailgate hinge has been flexed one too may times. I've read about the symptoms, but have yet to deal with it first hand

What is the most prudent repair for this problem? I seem to think I've seen rear wiring harnesses, but I feel a little silly buying a whole new harness when the problem is a small bad spot.

Has anyone just cut or replaced the bad spot? I've tackles much larger problems on my Amazons, but is the replacement harness the *best* fix? Could the problem be something else altogether?

Also
I had my front bodywork off for cleaning and re-sealing of one of the plastic headlight lenses. I noticed that the intake for the air box is this crazy-tall snorkle arrangement. Is that what people replace when they do the 'air box mod'?? Does reworking this thing result in the minimal mileage increase from better air flow?

Thanks as always.