HELP!!!! '87 Supra idle problem

[Morpho]

I got an 87 Supra that has an erratic idle...goes up and down between 1000 and 2000....similar to the problems posted by kewlcoconut. initially, the code read a bad tps and starter signal...i guest the car had been jump started to get the starter signal...the tps was replaced but the problem didn't go away(code went away though). Replaced the O2 sensor and a new cat. I've checked everything...idle speed controller, airflow meter, sensors(temp and coldstart) checked all the vacuum stuff, egr valve works fine..vacuum to pressure regulator is good too! checked the distributor pickup coils, checked the wiring from the sensors and components to the ecu, thought it was the ECU so pulled one from a good car and still couldn't get it to work. the only way to get the idle down was to reduce the size of the throttle bypass(the line from before the throttle body going to the idle speed controller) but this causes the car to continue to run rich....so it still won't pass california smog....help!!!!!!