I have a 94 integra with a GSR, the idle is around 1000 rpm, when I turn the ac on it drops down to less than 500 rpm, almost to the point of turning of, and the car feels like its going to die in any second. Also the rpms seem to become slugish, and the vtec is not kicking in at any moment past 5000 rpm. Please help

I have replaced :
Fuel filter
Coil pack
Spark plugs
Wires
Idle air control valve

Have the injectors and the upper intake professionally cleaned and recalibrated.
Idle learn will likely need reset along with shift adapts.
What fuel are you running?
Has there been a "chip" installed that could affect any of the symptoms that you describe?

Have you tried replacing the alternator?

That's what it sounds like to me when you talk about the AC sucking power.