Dave,
I found this explanation on the web.

"Adjustable air bleeds, while usually found on high-dollar fuel mixers, can have a significant impact on A/F ratio. Not only will larger air bleeds lean out the mixture, they will also delay the effect of that circuit by weakening its signal.

Conversely, installing smaller (richer) air bleeds boosts the signal and speeds up the transition into that circuit. These factors have great influence over driveability."

In my case, since the mains are not starting until apx. 3000rpms, and I need to richen the transition circuit, by installing smaller idle air bleeds will do both. They will richen the transition circuit and also speed up when the main circuit (primary jets) come in to play.

This O2 kit is a great learning tool. I am finding out why I have made changes to my jetting in the past and not received the change that I was looking for. I thought in the past that the main circuit started around 2200rpms or so (per QF. But this is with the stock setup which mine is no longer.) and now once I chart out the rpms and the O2 readings, I can see the jump in the mixture reading that shows me where the main circuit now starts. I am curious how much lower the main circuit will now start when I change from the .075 IAB's to the .071's. I will show my changes once they are known later in the week.

Thanks for the reply.