Yeah, I would also like to know about the idle control relay, although I got this feeling that W126's do not have it, or at least my 280SEL does not have it. After replacing my idle control valve 2 weeks ago, it has helped stabilise the low idle speed a little, although there're still little vibrations at idle, which I hope to eradicate somehow.

Anyone knows anything on this idle control relay on W126s?
Part number is greatly appreciated!
Mervyn