help needed with picture

[theclash]

the green plastic plug in this picture has corroded and if i put my finger over it i can feel it sucking in air is this right or should it be blanked off.    its on the opposite end to throttle body (fuel intake i think)
     
 its a 92 8valve

[maxp]

No it should be blocked off.
You can actually buy the caps from vw still.

I would do this as a priority as that air should be diverted into a one-way valve (follow it round, you will see it) which is used to aid braking.

[theclash]

thanks maxp found it by accident while trying to sort my irratic ideling, i will have to order one.