Moki the vent is the small hole in the side of the square plate with the circular raised section. When a problem with mixture is encountered inside a cowl it can be rotated to a different direction. If that doesn't work a 1/8" brass tube can be soldered to it and a length of fuel line run into the inside of the fuselage etc. If you search the tread there are a bunch of posts and pictures on how to do it.