Actually, that area is part of the fuel bowl of the carburetor. The rods going down in the fuel are your secondary fuel metering rods. When the secondary throttle plates open, air is drawn in causing the butterfly to open and raise the metering rods allowing fuel to flow into the secondary bores. As far as the high idle, there are two different ways to adjust it, depending on the series of the carburetor. Most common, there is a high idle adjusting screw on the cam, the other way requires to bend the high idle cam rod.