Check out this nifty toggle valve. It has the exact port configuration you need. Hook the "common" port to the SOV, the exhaust to the air and the other port to the vacuum source.

Clippard Brass Toggle Valve w Hose Barb Fittings Panel Mount | eBay

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-Evan


Benz Fleet:
1968 UNIMOG 404.114
1998 E300
2008 E63


Non-Benz Fleet:
1992 Aerostar
1993 MR2
2000 F250