The drawing is generic, Carter made hundreds of different YF carburetors.
The threaded tube is the idle jet. It should be reinstalled from whence it came.
The pressed plugs should NOT be arbitrarily removed. These are access plugs. If compressed air can be blown through the passageway covered by the plug, no need to remove the plug.
The pump check valve is off to the side from the idle jet.
Threaded plugs would have added significantly to the original cost of the carburetor.
Jon.
