avs air fuel adjustment screw

im running a 750 avs on my 360 and i only have one screw to control the air/fuel adjustment. The spots where they usually have them are blocked off with plugs. Ive been told this is so you would have to bring it to the dealership to get it fixed but i dont know. i was just wondering where my one screw should be set at. right now i have it one turn out.