Was checking vacuum connection and found this part not connected to anything.

The numbering on the part isnt clear so I couldnt look it up. Any idea?

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Sure helps to know what car and what engine...

__________________
Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

plug looks like a low oil level sensor plug