Thanks again to everyone who offered advice for this issue. I'm cautiously optimistic that I figured it out (by accident). Early on, I questioned the one-way clutch of the alternator pulley causing my symptoms due to the amount of belt flutter I was observing. After replacing the pulley and belt tensioner, there was no change. Fast- forward to last week... the alternator (original 90 amp) shit the bed entirely so I replaced with a new 150 amp Bosch, and the idle seems to be back to normal. Again, cautiously optimistic but it sure seems like the uneven idle is now corrected by the new alternator. Fingers are crossed. P.S. the top, forward bolt of the alternator is my new least favorite fastener on the vehicle.