Thanks Frank,
This is very helpful information. I'll follow the gas vent line back and will hopefully find the junction and take the front part off. I can put something on temporarily, a screen until I'll find something better, close to original.
I guess the line's screen was designed for creating a balanced atmospheric pressure for the air volume above the gas level? This means that mostly gas-air mix might come out or in rare occasions air move in.
Dirt should not enter the line...I guess a foam filter might work for the time being?

I was moving the 500SEL on the lift this evening and will have a look over the weekend and find this vent line.

The other smaller line to the air intake: I have lost that line. It was not on the car. The location where that line could have ended [at the air intake as you mentioned] could be at the right engine bank's valve cover rubber hose to the air intake. That hose (finger thick ID) as a small T for a vacuum line.
Is this vacuum line the small vent line connection from the charcoal canister?

Exhaust : I'll check how the two down pipes are connecting and take pictures.

I'll be back soon.

Thanks again, Martin