Mine is connected to the firewall too but just hanging above the bell housing of the trans.
I imagine it is a drain for water off the windshield and the wiper area.
I guess to determine this just pour some water on the windshield and see if it drains out of the black rubber tube.
It is not connected to anything on my 04 either.
Note: good observation as I didn't even notice it when I installed my CAI.

PS ...
There have been problems with the na Crossfires getting a check engine light (CEL) after installing the Needswings CAI.
It may not happen right away but it has occurred on 5 Crossfires now.
There have also been issues with rough idling.
Rob is aware and has been trying to determine the cause.
He is keeping us up to date here