I have a 2007 CTS-V and all of the other V's I looked at did not have this tube (2006 and before). I am planning to change the intake tube but I need to know what this is for before I change the tube to see how it needs to be connected or if I even need it. I would guess it's for a sensor but I haven't torn into the car to figure out where it's coming from.

See Link (Thanks for the pic CaliCadi):
http://i188.photobucket.com/albums/z310/calicadi/Hoots-0507-8.jpg

Any help would be appreciated on this one.

Hrm...If I had to make a wild guess, I'd say it looks like a cold startup air pump- they pump air into the intake on cold startup to reduce emissions, and shut off after a few minutes.

If your right this would be one of the things I would concider next to useless and sounds like something I could eliminate.

I will run it back to see what it connects to and if it looks something like an air pump then I will do a "test" to see if it effects the operation of the V. If it works without I will keep all of the parts to put back on when Smog is required.

PCV tube.

PCV tube.

Not sure this is correct but a good guess. I thought it was the PCV also but there is no oil inside the tube and I see oil in the inside throttle body (intake manifold side). Plus I have seen where the '04's and 05's have been connecting the catch can and I do have a hose in the same place.

Only 5K on the car so I'm pretty sure the oil isn't coming form the heads, it must be blowby from the PCV.

Air pump sounds more likely or maybe a sensor is connected to the other end of the hose.

Stageup is on target, this tube vents blowby back into the intake track.

Stageup is on target, this tube vents blowby back into the intake track.
I checked it out and I see the tube going into the Valve cover, I feel like an idiot.

Stageup, I apologize and thank you for the help.

BTW, is it cool to put a filter on this line or should I continue to feed it into the intake?

Actually it is not a PCV tube, technically.
It is part of the PCV system though.
On the rear corner of the left valve cover will be where the PCV is, this tube is a "fresh air" tube.
It uses air from the induction system to equalize pressure in the crankcase as the PCV draws air out of the other side of the engine.
The air in the inlet tube is nice clean filtered fresh air so they go there for it.