Start with a set of sparkplugs and these:
http://catalog.worldpac.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=catalog.mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=1XC0ZKQX926C15SG0A&year=1995&make=MB&model=C-280-001&category=F&part=Spark+Plug+Connector
You could well be right about the egrflow, if the vacuumsource to it is not connected.
May have to have a look at a vacuum diagram, to see where the line is upposed to connect to.

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2007 C 230 Sport.