New air intake/vacuum hose
 

Hello. I put a new air intake/filter on my C5 a few years ago. Then I got cancer and never finished install. There is a vacuum hose that I don't remember where it goes. New intake plenum doesn't look like it has space for it. Car runs fine without it plugged in. What is it, and should I drill a hole for it?

Your best bet is to find another C5 and see where it's connected on it.