I have chronic high idle problem that comes and goes.

Ist you need to hook an analog ohm meter to the data conector and see if you get any codes.
The 2nd fix is to put the right thermostat in. It must be 195o for the temp sensor that talks to the ECU so the ECU knows what the engine is doing.
A bad O2 sensor could make it run rich,,,but not as rich as your discribing.
The ICS could be bad ,,,and this does not give a trouble code to the ECU, so it has to be removed and tested.
Mass air flow sensor or the TPS/idle switch could be bad. These will give codes.
You could have an extra sensitive sniffer , which is a good thing,,,after I went thru chemo any toxic fumes get to me. A good sniffer is the normal natural state for us before the industral revolution desensitised most of us.