I dont have a part number, however, the change over switch is the one mounted to bottom of the manifold and has 2 electrical connections and 2 vacuum connections one vacuum to crossover flap and other to the manifold flap. Each flap has a microswitch with an electrical connection. I think this is where mine was damaged.

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Dennis
2006 E320 CDI Black/Black Leather. Nav, HTD Seats HK stereo 32000 miles.
2000 VW Passat 1.8t 300,000 miles as of Dec 09, 2009 original owner
1997 E300d Silver 300,000 miles As of Jan 05, 2010
3rd owner SOLD