Known faullty parts , specially after they have been moved.
Cheap and recommended with plug change.
This ignition system is a waste spark , meaning two plugs fire in series ,
[ which is why only 3 coils for 6 plugs] so a bad connector can affect two cylinder misfires. The connectors on the other plugs do not suffer the heat encapsulation the coil ones do, and they also have a snap connector, whereas the coil onder ones are a friction/pressure spring fit [ not to anyones liking]
So the others do not have the common fail rate as the three I recommend changing.
Newer systems have coils on each cylinder .
That's why...
http://catalog.eautopartscatalog.com/mercedesshop/sophio/quote.jsp?clientid=catalog.mercedesshop&cookieid=1D00YU6RY1IL0R2S31&baseurl=http://catalog.peachparts.com/&partner=mercedesshop&year=1997&product=F1010-84561&application=000357357
More details in the archives on these ... enough to fill a NYC phone book.. (: