Thanks for the replies....but I still can't find it....there are essentially 2 firewalls in my car...one that is close to the engine....and then another that is the cabin wall. I took off the large plastic cover ( the one that hides the cabin air filter) so I could get a good look at the brake booster...and there is nothing anywhere near it that resembles a vacuum switch...There is definitly nothing there that has a green vacuum line going to it.....
Troubleshooting is my goal...and I need to resolve this becuase I have to go have an emission test.....

Anyone got a picture?

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1995 E300 Diesel
1994 E320
1999 C230K
1994 S500 W140
1990 300 SEL