1990 560SEC fuel injector holder

[max&vita28]

The new fuel injector holder I purchased has a hose bib on the side.
Will someone please tell me what it is for? I haven't worked on the engine
yet.
Thanks

[hookedon210s]

It is the connection for the aux/idle air distribution hose. You will likely need to replace this as well as the related hoses because these get hard with age and will split during replacement of the injector cup. Mark