Surges at Partial Throttle

[Comatose]

1986GT, mods listed below. 167k on the motor.

If I try to hold the motor at 1200-1300 rpm, the car surges between 800-1600 rpm, when it's cold it does it quite severly, when it's warm, it still does it, but to a lesser extent. The car starts and runs great. Any ideas?

TPS voltage is .95v, IAC is disconnected, fuel filter was replaced about 5k miles ago. The car idles at 750-800, smoothly, no surging. Also, if I rev and hold the motor at 1700-1800rpm or more the car doesn't do anything out of the ordinary.

BTW--The with the IAC plugged in, the car bucks and idles too high most of the time. I've looked for vacuum leaks and found none. I have yet to try to pull codes.

Thanks for the help.