I cleaned and tightened all the grounds I'm aware of, under battery tray, firewall by PCM connector, etc. System voltage is 12.5 VDC off and 13.9 to 14.1 VDC w/ engine running, depending on load,so alternator output would seem to be OK. Curious, why do you suspect alternator?
( I understand your suspicions about ground gremlins!)

I forgot to mention in my first post that the car has had the cat converter recall done.

Former, now returned CEG'er! 95SE MTX, (AKA "The Road Rat"). Stock except for:TH fix, B.A.T. big brake kit, tranny cocktail and lots of re-insulated wiring! May yet be a 3.0! "Speed doesn't kill, stupidity does!"