The issue is NOT platinum electrode versus conventional copper core nickel electrode!

IT'S THE RESISTOR!!!!!!!!!!!!!!!!!

OE Mercedes plugs from the era of our cars DO NOT USE SPARK PLUGS WITH EMI RESISTORS.

Installing ANY plug that has a conventional EMI resistor, which is the common type for most cars, and REGARLESS OF ELECTRODE DESIGN, can cause driveability and/or emission problems.

Stick with non-resistor plugs, which pretty much limits your choice to the Bosch Super line. Parts establishments that cater to Mercedes owners (like Fastlane) should have the correct non-resistor type spark plugs. Most of the chain part stores WILL NOT have them in stock, and they may not even be able to order them.

Buy the non-resistor Bosch Super plugs listed in the owners' manual like H9DC for M103 engines. Don't buy the HR9DC. It has an EMI resistor - the "R". Most resistor plugs have an "R" in the plug type nomenclature.

Duke