Make sure you don't have any vacuum leaks. The TPI manifold has a tap in the back and one underneith that are easy to overlook.
There is an idle calibration procedure for the TPI. You might check out http://www.thirdgen.org
for additional details. Here is what I recall about the recalibration procedure.
*Remove the Idle Air Control motor (IAC).
*Put the ECM into diagnostic mode - I believe shorting the lower right two pins on the diag connector will do this.
*Turn the ignition on, but do not start the motor. The IAC motor should extend fully and then step back to it's baseline position.
*Turn off the ignition, disconnect the IAC and remove the diag shorting plug. This will leave the IAC motor in it's basline position.
*Reinstall the IAC motor with it's wiring disconnected.
*Start the engine and adjust the idle hard stop for some specified RPM (800 I believe).
*Use a DVM to measure the TPS voltage and adjust it to some specified baseline value (somewhere around 0.75 volts I think).
*Stop the engine, reconnect the IAC and your done.
Any vacuum leak will seriously upset the idle control. Unplugged ports are one common source as I mentioned above. An improperly connected PCV system is another cupret. Seems like it is real easy to connect the PCV to the wrong port on the left side of the TPS manifold.
Hope this helps although I can't swear by my procedure or the calibration values. The thirdgen site or a good service manual should clear that up.