Where the throttle is located just to the left there is a brass looking pin sticking out,dont know if its an adjustment or a place to hook a spring doesnt show in the papers that came with the weber. My carb is the DGEV that goes on the Mazda B2200
That's a plug screwed into a vacuum outlet, I believe.
Might be intended for the EGR, but many of us use an EGR block off plate instead, or just plug the vacuum line to the EGR and use it as the block-off (assuming that the EGR's valve does close completely).