the adjuster with the black knob in the picture below adjusts the slide height. The airscrew is the brass screw below the slide height adjuster. This screw is commonly referred to as the "air screw" and it meters the amount of AIR in the idle mixture, therefore turning the SCREW out will lean the mixture and turning the SCREW in (clockwise) will richen the mixture. To adjust it Set the air screw to 1 turn out. Start the motor Set the idle with the idle screw as low as you can NOW, TURN THE AIR SCREW OUT to raise the idle. If the idle goes too high, lower it with the idle screw. In other words, use the air screw to raise the idle as high as you can, then correct it with the idle screw (slide height adjuster) The slide height also affects the idle mixture as raising it allows more air in under the slide, so you would screw in the air screw to richen it up. You may have to go back and forth till you get the idle you want. Once you have that then you can go test it and then if your still having issues we can go adress that. There are 3 steps to adjusting these idle, (slide height, air screw, Pilot jet) Then needle height, (1/4 to 3/4 throttle) then main jet. The extra hi speed fuel jet can complicate the main jet requirements but we will worry about that later.