Loose Vacuum Line 1998 C280 (M112 V6)
 

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?
Attachment 132739

The vacuum solenoid operates the intake manifold resonance flap.

https://en.wikipedia.org/wiki/Variable-length_intake_manifold

Thanks for the info. The vacuum line hooks underneath the intake manifold and is pretty difficult to access. For now I plugged the hole and teed the vacuum line into the EGR Intake Pressure switch sensor line. Not sure if it works or not. At least the engine idles better with the vacuum leak stopped.:)