Can anyone explain what this is and what it does?

[SonicSVT21]

I am replacing some crumbling vacuum line and ran across this. Part number is D6TE-AA and google comes back as a thermactor. Can't find anything about what it does for our cars. This looks plugged to be so I don't see it doing much.

 

[99riocobra]

I believe it's a test port of sorts. You can remove it and plug it at the source.