DodgeForum.com - '97 1500 5.9 generator light

Hello y'all... I'm having some trouble diagnosing some electrical issues with my 97 Dodge Ram 1500 truck and I'm hoping y'all can assist me in figuring this out.

I started my truck up and immediately it didn't sound right, which was my first red flag, but I then noticed about 5 minutes later after driving the "gen" light came on and the gauge inside reads far less than the average 13.8-14,8 volts (roughly 8-10v on the gauge) and all the interior/exterior lights and electronics lose a significant amount of brightness/power.

After hooking up a multimeter with the truck off, the battery reads around 12.3 volts. Once I start it the voltage reads roughly around the same, but turning the lights on and heater full on, voltage drops to around the even side of 11V on multimeter (8-11V on the gauge). Revving or driving at RPMs above 3000 increases the V reading to around normal, but I notice there is a power drop when idle and the light comes back on. Alternator is new about a year old, ECM was replaced roughly the same time as alternator, and the battery is about a year or two older. 156k on odometer.

Any hints or advice on what may be causing the low voltage or gen light to turn on? From what I can gather it's a) alternator, b) battery, c) PCM/ECM, d) a blown fuse, e) some other clusterf*ck. I have a fairly limited knowledge of the electronics of a vehicle, so I'm at a disadvantage, but any help would be incredibly welcome .