The late S320 (M104) has waste spark system, one coil
on 2 cylinders. The plug wires you are seeing should then
be the low voltage ones. 3 of the spark plug connectors
have coil and the other 3 have not. I think the three
plugs under the coils are common to fail over time on a M104.
There is even a diagram on the black cover thats over the plugs.

Waste spark;
http://en.wikipedia.org/wiki/Ignition_coil

Coils and suppresion plug;
http://www.detali.ru/cat/oem_mb2.asp?TP=1&F=140032&M=104994&GA=722%2E368371%2C502508%2C605&GM=717%2E454&VIN=%2A&CT=M&cat=520&SID=15&SGR=060&SGN=03

More;
http://www.peachparts.com/shopforum/showthread.php?t=156872&highlight=104+coil

br,
syljua

__________________
1998 CL500 W140
1984 230E W123