Hi all, I have included a picture of a part of the throttle linkage (sorry don't know the precise name of this part but it's the bit in the centre of the picture) and it is variable being threaded b/w two nuts.

I have looked in my various manuals but can't find how it is meant to be spaced from the top/bottom nuts. Is this measurement crucial and why is it variable? If it is important, anyone know the measurement (for a 4.2 Series 1) I should space it at?

Thanks as always for your generous thoughts.