(This is straight from the horse's mouth)
First of all, you're not supposed to adjust the set screw on an Accufab throttle body. It is adjusted from the factory and they direct you not to touch it. You'll find that everywhere on the Internet, but you won't find how to set it back if it was inadvertently messed with.
I emailed them the other day and this is what they told me.
"With the TB off the car, hold it up to a light source (not directly into the sun however) and adjust the screw so that the blade has an "air gap" all the way around, top, bottom and sides, that looks as equal as possible. That's it. You don't need a feeler gage. Eyeball is more than adequate. " At first, you'll have the plate all the way closed and will see no light thru it to the other side. The top and bottom of the plate are set equidistant from the inside of the throttle body. You simple adjust the set screw until you have the sides of the plate matching up with the top and bottom. You'll see the same amount of light all around.
If you go too far, you'll have more light on the sides than on the top and bottom, and this will be incorrect. Same goes for if you don't go far enough and have less light shining thru than the top and bottom.
It will look something like this when you are done. The picture makes it look like it's a little too far closed, but it's just the camera angle making it look that way.
