2002 millenia S Vacuum purpose
 

Trying to find out the purpose of a vacuum at the end of a hose going to the manifold. I've been having a rough idle with TCS issues, P0105, and P1540. I finally traced a sucking sound down to the hardest vacuum line to get to its connector. I pulled the hose out and plugged it leaving the hard to get to conmector open and exposed. It's doing a little better now and the TCS isn't going nuts. I have circled below its location.

My question is, what was this vacuum lines purpose? Is it detrimental to be connected. I have driven 13 miles no issues after clearing codes. Can I leave this hose unhooked? Or should I try taking things off to get to it....which seems so fun.

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