Low output at idle w/ac on?

WHOA!
do a full field test.
Make sure the battery is up to voltage.
Put a voltmeter on it.
Disconnect the field wire off the alternator, it should be blue.
Run a jumper wire (at least 14ga) from the battery to the wire you just took off.
Start the car and check the output voltage, at idle, theb at 2000rpm..
Change your voltmeter from DC to AC and repeat.
return the engine to idle, remove the jumper, and reconnect the field wire
Results;
1)There should NOT be any A/C in the system which indicates a blown Diode in the Rectifier-section. The alternator is not yet junk, you can take it apart and replace the diode fairly easy........ if you can find a diode, lol.
2) As for DC output, IDK the factory specs anymore so I'll guess.
At Idle I want to see at least 2 volts higher than what the battery has at rest.
At 2000rpm, I'm expecting to see over 35VAC.

If your alternator can do this, look elsewhere.
like maybe the throttle-kicker.