They used non-resistor plugs due to the plug wires, cap, and rotor all have 1KOhm of resistance built into them. By adding more resistance to the mix using a resistor plug you will not get the required spark, at least not all of it. Therefore you may not burn your air/fuel mixture as efficiently and thus waste gas or put more carbon in your combustion chamber. I have used both platinum and non-resistor plugs in my 190 and I can tell you there is a difference and the non's work better and the engine runs better. I also switched to NGK wires as they stay within spec warm or cold where I found Beru and Bosch that did not.

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~Jamie
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2003 Pewter C230K SC C1, C4, C5, C7, heated seats, CD Changer, and 6 Speed. ContiExtremes on the C7's.

1986 190E 2.3 Black, Auto, Mods to come soon.....