Ha, you found your vacuum leak! The green plastic hose is the vac supply for the Climate Control. The red/gray is for something else (I only have two gas engines, the rest are diesel and they are different).

You will have to get anything but simple straight bits of rubber hose from a dealer or good independent MB mechanic, they aren't expensive, but you wil have trouble finding the y and T connectors anyplace else.

Check the rubber hose bits for all the hard plastic lines, there are several (some go to temp sensors, some to valves, etc) especially those on the intake manifold. They are all in the same condition as the one you found, and replacing them will make a big difference.

The black line is a vent line, usually, and, and can be ignored.

Carbon fouling of the plugs indicates rich mixture or ignition problems. The ignition is probably OK -- new cap, rotor, etc, but you may want to check condition of the wires! If not installed properly, or not removed properly, they will be broken inside and not working properly, and this will cause bad running, fouled plugs, and eventually a roasted catalytic converter. Don't play with them with the engine running, as the voltage can kill you if they are leaking badly.

NKG is a perfectly good plug, but check that the heat range is correct. Also, make sure this is carbon and not oil residue, as worn out valve guide seals will cause fouling and misfire, resulting in plugs with black deposits over brown/gray crud.

A leaking cold start valve will cause rough idle, throttle lag, and rich idle, too, from unwanted fuel running into the manifold.

The bad news is that a bad fuel distributor can make the car run rich, and the only cure is a rather expensive replacement, you cannot fix them.

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!