If you get a Haynes manual, it will give you a ton of great info, and answers to questions like this.
I dont have any pictures available atm, but there is a 'mixture screw' of sorts on the side of the AFM. It might have a small rubber plug covering it, or it might not. Should be on the drivers side of it, sort of near the bottom on the side. You can play with that to get a bit of mixture adjustment. There are other ways as well that I havn't used.