These go between the coil and the plug , so there are only 3 of them...it is very possible they were overlooked b/c you can not see them until you pull the coils off each plug and they usually stay stuck to the coil.
They are the MOST COMMON failure part for mis-firs on 104 engines with DIS.
and most Benz Techs just routinely change them when they change plugs b/c they are aware of that.

And these engine do not run well with Plat plugs...but that is another
Benz Tech known thing.
I would not expect a regular guy to know either .
Take a look...

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A Dalton