Raise 91 300E Idle Speed? Purple wire trick?

[OrangeGuy]

When warm my 300E idles at just under 500rpm. While it is very smooth and quiet, my 250K mile engine has about .2-.3 bar of oil pressure when hot. The manual does state this is acceptable. But an rpm increase of 50-75rpm would bring that closer to 1 bar and make me feel better. I've read about the "purple" wire trick to fool the ECU to raise the RPM by maybe 50. But I've only seen early 86-89 cars referenced. Does this trick work on the 90 and up W124 too? Which have slightly different ECUs than the early models. Anything else I could do?