Ah yes, can remember that.... The only way I got to it was by removing the whole throttle plate housing...4 nuts and linkage. As it turned out, I think this made the setting easier to do having it on the bench...then just reinstall. This and the whole job is well referred to in Graham's guide here.

http://www.peachparts.com/shopforum/attachments/vintage-mercedes-forum/73989d1257435944-73-450se-should-i-replace-intake-manifold-seals-adjusting-cleaning-tps-r107-mercedes.pdf