I'm sure this has been discused but,

Does the idle screw effect the fuel or the air?  If I turn the idle screw all the way in am I cutting off the air or the fuel - Does turning it in make it richer or leaner?

Thanks,
Paul

Are you talking about the knurled knob on the long post between the carbs - the one you mess with to adjust the idle?

If so, maybe this will help.  Turning this knob doesn't do anything directly to the carbs - neither air nor fuel.  What it does is move the "stop" for the throttle cable.  When you twist the throttle grip -- even a little bit -- you pull the other end of the cable away from the "stop" and the idle screw no longer has ANY effect.  When  the throttle grip is twisted all the way forward (off), the position of the idle screw determines the minimum amount of throttle that is applied at the carbs.

In light of this, your "larger" question becomes something like, "What happens when I twist the throttle?"  As far as I understand it, more throttle means more air, which results in more fuel vapor being sucked through the jets and getting mixed with the air before being pulled into the cylinder.

If your original question was about the pilot screws on each carburetor, I apologize for warming up the atmosphere with my hot air....

The way I understand it, if the screw you adjust is upstream from the slide it affects the air through the idle circuit and if it is downstream (a la the GS500) it affects the fuel.  So, winding the screw in makes it leaner by restricting fuel flow and winding the screw out makes it richer by allowing more fuel to flow.  Remember this is only the idle circuit and doesn't affect fuel or air flow once you open the throttle.  What Kerry said about the big knurled thing between the carbs that you adjust the idle with when you are stopped at the lights is largely tru.  If you wind that one in what you are effectively doing is opening the throttle a small amount, and as Kerry said, keeping it open a small amount even when you fully wind off the right handgrip.  Hope this answers what you needed to know.  
BTW, thanks again, Kerry for the Avatar hosting.