The oscillation or "hunting" as you'll see it referenced as in the CIS threads usually mean that it's too rich. When you're adjusting the idle you have to adjust the air set screw as well as the mixture screw. If you just turn the idle down, you're decreasing the air that can get past the plate, but using the same amount of fuel so it will then become rich. To decrease the idle turn the idle down and then lean the mixture out, but remember to always turn lean to rich. Confused yet? The way I understand it you need to go too lean, then richen it just a hair because they spec that all adjustments be made lean to rich.
I could also be wrong about all this, but this is what I seem to recall reading and what has worked for me. But it's getting late and I'm overly tired.
If you want the Bosch CIS book as a PDF let me know and I'll post it for you. I also found these threads helpful.
http://forums.pelicanparts.com/showthread.php?t=232089&highlight=cis
http://forums.pelicanparts.com/showthread.php?t=185926&pp=20&highlight=cis+mixture+idle