...welcome to the forum cakestep!!..
![Grin ;D](https://www.kymcoforum.com/Smileys/default/grin.gif)
..i think that screw is used for reading engine emissions...
..only thing i can think of anyway...lol..
..i ran with mine out for a while, sounded good initially, but the more i heard it, the more it sounded like an exhaust leak...lol..