1994 E320 Resonance Intake Manifold Switchover valve - Vaccum connection???

[BMG]

I had the Resonance Valve out of my car this weekend to work on the ETA. On reassembly, I was rehooking up all the vaccum and electrical connenctions and noticed a vaccum nipple next to the electrical connection for the Resonance valve.

I did not have any vaccum lines laying around inside the engine that went to this. I got under the engine and visually followed all vac lines including those to and from the tranny. I searched the vaccum diagrams and did not see any vaccum lines leading to this device on the schematics. The nipple still is shiny indication it did have a hose on it recently.

I did take a length of Vac line and connected it to the unit. I ran the engine and did not notice any suction or hissing from the hose. I drew vaccum on the hose and did not hear any change to the engine.

Is there a line I am missing?

Thanks

Brian