Another not so brilliant question, all. In my '77 240D, there is a clear, plastic tube that comes from the vacuum pump and runs to the top of the air filter. On the air filter end of that tube, there is a connector. Could one of you illustrious gurus please tell me what the bloody thing is called?

I've attached a picture below and added and arrow for clarity. Disclaimer: I've lifted this pic from an old thread on the site. It perfectly shows what I'm trying to point out. If that is not allowed, please delete and accept my apologies.