"So when you are taxiing at 900RPM, and you pull the mixture out, you are not reducing the fuel provided by the carburetor idle circuit, but you ARE reducing the fuel provided by the carburetor circuits that provide fuel flow at higher throttle settings (butterfly more open). This reduction in fuel flow, and slightly higher combustion temps, can help keep you plugs from building more lead in them and therefore fouling."

I disagree. If you taxi @ 900 RPM and pull the mixture back what happens? The motor quits! You just reduced the available fuel for ALL the jets (fixed runs/orfices) in the carb/FI unit including the idle circuit.
The mixture knob controls ALL fuel flow to the carb/FI unit low, mid and high. The same knob that leans the mixture for taxi on the idle jet allows you the lean for best mixture thru the main jet(s) in flight.
Try this for yourself: Start the motor. Allow it to warm up. Now pull the mixture back to the point the motor starts to quit at idle and then give it just enough mixture to make the motor run smooth. You are now idling at you leanest idle mixture you can (highest EGT).
Now; without touching the mixture knob, try and advance the throttle. The motor will die. What you have just found is the mixture knob DOES control the fuel that is availible to ALL the jets in the carb/fuel servo including the idle circuit.

Again; the throttle butterfly is controlled by the throttle knob and thus control the amount of AIR going to the motor.
The mixture control controls ALL orfices available to put fuel into the venturi. High and low it's the same control.


You can kill the motor at any throttle setting using the mixture control.


Chris