190E fuel adjustment knob

[ssanmor]

Hello all.
I was curious about the 7 position selector besides the ECU, similar to the one that is near the ABS in order to select the type of fuel, marked with "S" and "N" positions.
I have read in Vivid Workshop CD the schematics of the engine management, and that item (the one marked with pos "1" to "7") is called something like "fuel equalizer", and is only a resistor. It says that its function is to adjust the air/fuel mixture ratio. Does anyone know what it is really for?

The factory default pos is "1", does anyone know if that corresponds to the richest or to the leanest mixture? Can anyone check in a MB official manual? Is that the famous R16? If so, it seems not to be for the timing adjustment, but for the mixture adjustment, right?

That knob is tamperproof and present in more models, some 190E's (including 16V) and 230E, for example.

Thanks