Stojan - this is a page you should add to your library
ignore section 10.6 at first, what you need is at 10.5
The butterfly is the brass plate inside the throttle body. When you remove the rubber plumbing, you will see it at the throttle body opening. Move the throttle cable and you will see it open. At first I would not necessarily remove the throttle body, just get in there with some carb cleaner and a rag and thoroughly clean the butterfly and throttle mouth. After cleaning you adjust the gap to .002"
If i remember correctly, you adjust it with the throttle cable stop.
DO NOT change any other settings, just do the cleanout and set the butterfly then see the results.