Maybe I'm blind or stupid or just lost but where is the idle screw on the a6.

 

follow the air intake tube straight into the throttlebody. When you're looking straight at the opening of the throttlebody, the idle screw is at the top left-hand corner of the TB, just above the intake tube. It may help to pull the intake tube off to get at the screw. And make sure that after you set the idle screw, you stick it down with some grey silicon. Otherwise it'll wiggle back out, adn you'll be tweeking the idle every time you drive. Go ahead, ask me how I found that out

 

is it the flathead screw

 

yes, about 3/8 of an inch in diameter.