Most of the tests I have tried to run so far were done WITH THE HEATING ELEMENT REMOVED.
I am mainly using the write-up at
Warm up regulator (WUR) Calibration - Benzworld.org - Mercedes-Benz Discussion Forum
It seems to be more detailed than than the "Playing with your K-Jetronic Warm Up Regulator, or WUR" write-up.
I only eyed the o-ring to find a replacement; the one I found that fit
seemed to be about the right size. I could not tell 100% from the old one because it was semi-flattened.
I have contacted Roger and he is sending me one of his CIS kits later this week. Hopefully it will be exactly what I need. I have done anything since last week because the one I currently have leaks all over the place.