The advise from the techs is unanimous.
All MB's made before 1997 were designed to run on plain Bosch or Beru copper plugs. They just run badly on platinum plugs.
Many techs on this site are reluctant to answer bad running / idleing questions if the car has platinum plugs.
Also, there have been others on this site with hot running issues that weren't solved until the radiator was traded out.
2001 E430, Bourdeaux Red, Oyster interior.
1973 280SE 4.5, 170,000 miles. 568 Signal Red, Black MB Tex. "The Red Baron".