its called the "evil vacuum servo"...was used on the W123, W116 as well as the W107 (and possible a couple others) it was designed by chrysler who used it 10 years before mercedes did...and there are no kits I am aware of for a DIY.

__________________
Proud owner of ....
1971 280SE W108
1979 300SD W116
1983 300D W123
1975 Ironhead Sportster chopper
1987 GMC 3/4 ton 4X4 Diesel
1989 Honda Civic (Heavily modified)
---------------------
Section 609 MVAC Certified
---------------------
"He who fights with monsters might take care lest he thereby become a monster. And if you gaze for long into an abyss, the abyss gazes also into you." - Friedrich Nietzsche