My 190E 2.3 also has that resistor, I think.
It has a EZL resistor marked "S" and "N", I suppose that's R16, is connected to the ignition controller and perhaps it controls the ignition timing.
BUT behind the battery, connected to the fuel ECU, there is another similar knob, with pos. marked from "1" to "7". It is currently in pos "1". Is that R17? I suppose so.
Does anyone have official information on this resistor?
My Vivid Workshop CD says it control the mixture, and that the default pos. is "1", nothing more.

Thanks!