I use the choke on mine, but oddly enough the fuel meter shows this slightly leaning out the mixture. Bumps the idle speed slightly, though.

The only adjustments on the Weber are the idle mixture adjusters and the idle speed. All the rest of the tuning consists of swapping jets, air correctors, and emulsion tubes (although I think you can adjust the float bowl levels slightly which affects all circuits).

There is one idle adjuster per carb - syncronizing the front and rear carbs is even more important that with your typical SU setup because there usually isn't a bypass tube between the two carbs - so if one carb is closed it will miss on those cylinders.

The idle mixture adjusters are on each barrel - and control how much gas goes in with the carb at idle - the adjustment makes very little difference at any wider throttle setting. Setting these involve getting the engine nice and warm, syncronizing the idle adjuster so the idle speed is correct and the same amount of air is going in each. Then just screw those valves in and out slowly, and leave them in the spot that results in the highest idle speed. Too far in and the cylinder goes lean, too far out and that cylinder goes rich. It's fairly subtle since only one cylinder is affected, not two at a time like tuning SU's. Again - this just fine tunes the amount of gas fed in at idle to accomplish a sliky smooth idle - crack the throttle a little and gas starts flowing through different circuits and the tuning of the idle circuit makes very little difference.