SOLVED:
OK so after weeks of messing about, getting the alternator checked and rechecked, nothing seemed to work.
There was a bad diode, which I got replaced, but I was still dogged by the same problem.
Then I fliiped open my downloaded copy of the tech manual (thank you torrents) and discovered that the wires for the voltage regulator connector were switched somehow.
Simply switching them over has solved my problem.
Of the two wires in that connector, one is the alt sense, which is always hot, and the other is the reference voltage wire for the regulator, which turns off when the car is off. With the wires being switched, the reference voltage pin was always hot, and that caused the slight whine/him from the alt, as well as draining the battery.
Thank you all for your help.
