The 60x VCV isn't progressive in the sense of supplying a varying vacuum signal. It is "on" until the throttle reaches a certain position, then a rubber seal is pressed against the vacuum orifice by a spring. At WOT, the spring is fully collapsed and forced against the orifice for a positive "off". There are several writeups, including on this forum, of how the VCV works and how the vacuum signal is generated. On the turbo engines, the BUFO is there to create a vacuum signal based on engine load, not throttle position.

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Current stable:
1995 E320 157K (Nancy)
1983 500SL 125K (SLoL)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

Gone and wanting to forget:
1985 524TD 167K (TotalDumpster™) [Definitely NOT a Benz]