I dislike saying this, but disconnecting idle controls to get a better idle and hot start is a jury rig for emergencies. Wholesale replacement of the fuel and electrical controls will cause you to spend more on parts than a good diagnostic session. Put the meters and gauges on the systems and see what is happening. Some of the stuff Brian replaced is routine, maintainence-type stuff. Others, like the injectors, should only be replaced after testing.

What if your erratic idle is the result of a worn valve guide causing combustion leaks? What if it's a worn throttle body or a sticking control piston in the fuel distributor? As Hilton noted, accumulated crud, especially in the airflow sensor box and throttle body are candidates for service.

How erratic is the idle? +/- 50 rpm, 100, 200? An occasional miss followed by a brief surge?

Finally, since warm idle mixture is controlled primarily by the lambda unit, an exhaust leak in front of the O2 sensor can have an amazing amount of influence on the sensor. Essentially, the unit sees an entirely incorrect version of the exhaust gasses as the leak changes back pressure and (depending on the size of the leak) actual makeup of the gas passing by the sensor. Fix the big, obvious problems first, then go to the analysis and test procedures.