low idle speed issue when a/c on

hi all, my 92 automatic daily mule idles real low when in gear when the a/c kicks in.  i cannot determine how it is supposed to work.i vaguely recall there is a idle boost solenoid and they either are not reasdily available, or very costly.IF thats the case and the problem, then i would wonder if I could install a small nipple in the intake after the tb and install an air solenoid that comes on with the a/c clutch.car has 202k and runs like NEW. love a miata