In your engine, the resistance is in the spark plug wire boot, not the spark plug itself.

If you use a resistor plug (all platinums are resistor plugs), you are doubling the resistance, which is hurting the spark.

Just install regular copper core non-resistor plugs. They are cheap. Your car will run perfectly, and you need to change them every 30,000 miles.

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Paul S.

2001 E430, Bourdeaux Red, Oyster interior.
79,200 miles.

1973 280SE 4.5, 170,000 miles. 568 Signal Red, Black MB Tex. "The Red Baron".