[priobe]

In my findings yes you are right, however the way I see the operation is this:

The idle jet holder and idle jet fuel, combined give you a mixture ratio according to you motor. This combination carries the motor to about 2800 rpm or so. Maybe even 3200 rpm. You can remove the main stack and see where your rpm or motor stops running. The idea here is as the idle circuit combination carries the motor up to these rpm range the signal starts to become weak somewhere around 2200 rpm. This is where the emulsion tube plays it roll. The main jet is begining to engage probably around 2500 rpm. Now with the etube and main jet at this low rpm ranges the signal is weak but cuzing an effect to the mixture.

The mixture screws which I like to call volume screw control the amount of mixture to the motor with the throttle plates shut. regardless of the rpm. This is why when you crank open the "mix screws" volume screws on deceleration the back firing tends to go away. Your introducing more of the mixture