Hopefully this helps.

Here is the section I found in the online service manual that has diagrams.
https://www.startekinfo.com/StarTek/outside/11883/PROGRAM/Engine/107/M117_56/14-050.pdf

Also a lot of vacuum diagram info and schematics in this post:

http://www.benzworld.org/forums/r-c107-sl-slc-class/1453268-107-vacuum-diagrams.html

You just need to dig through to find your applicable chart as they are not in order.

I don't have a 560, but my first guess for that line would be to look for a thermal vacuum valve burried under stuff on the intake area. Valves usually have a single straight up connection off the top and another that comes off at an angle. They open and close by temp. Just a guess looking at it. As I said, don't have a 560 so no direct experience.

Hope the diagrams help!

 

Found the connector. In case anyone else will experience the same problem, I am including pictures.

 

Nice find! Hate those buried ones. Glad you were able to get it fixed