Brother of The Benz, pmizell
That is the air line to your electronic ignition's atmospheric pressure reference.
If you remove the airfilter and trace it under the fuel distributor, you will see it plugs into a rubber 90 degree fitting at the ignition system.
You can purchase this line in bulk lengths from your local M/B dealer's parts department.
Don't be too concerned if it is broken, everything will perform anyway until you replace it.
There are many lines of this material, but this seems to be the one that is short lived.
I couldn't keep from noticing you still have the hex nuts holding your airfilter top in place.
To make it easier to service the filter, I replaced mine with wingnuts. I bought them at Sears Hardware, maybe $0.15 each. I also replaced the two that hold the housing in place as well.
The small moulded hose to the rear of the large one is your possitive crankcase calibrated port. It too becomes hard and brittle, but you very rarily remove it.
You definately should replace the oil filler cap with the proper M/B cap and not that gascap. Not only does it seal properly, but it looks Super.
Happy Trails Beep Beep from The Spiderman in Houston!!!