I have found a loose vacuum line that is related to the unknown components below. Looking at front of the engine on the drivers side: The left ? is the loose vacuum line, the center ? is an unknown solenoid valve (or looks to be), and the right ? is a vacuum actuator that rotates a shaft in the intake.

Any help is appreciated. I need to know where the supply line connects and what this system's function would be?

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1976 240D
1987 560SL
2007 E320 Bluetec
1998 C280 (now son’s car)
1982 240D Manual - Sold