I think this rod is the source of my rattle, what is it and how do I tighten it?

[78F350]

I'm at the office and don't have a Boxster handy today, but I'd guess that's the pressure line for the power steering. Whatever it is, for it to be correct, it needs to be fastened to the underside of your car. Something has come undone. Pull the plastic panels off the belly and see what is damaged. Also, look up towards the engines where that leads and see if it is un-clamped.

If you make the effort to actually look at it and can't figure out what's wrong, I may jack up one of my cars to get some pictures of what 'correct' should look like.