Hey !!! I know what's wrong w/ mine now-I don't have a hose on the end of that pot to the right of the red " Circle" . Where does that hose go to . ? This thread is crucial . I'm going to get hose RIGHT NOW !
If you mean the brass colored vacuum valve- it's the a/c idle up system. The hose goes to a vacuum switching valve to the right of the headlight washer reservoir. It applies vacuum to the carbureator, which increases idle speed to around 1000 RPM if adjusted properly, for when your a/c compressor is running. It's non functional if you don't have a/c.