I don't mean to hijack this thread, since you are asking about the GM version and not any others.
I am also considering a CAI as well, but I don't like the one offered by GM. When I had my Z3, the after market CAI's had a heat shield. I was surprised to see that GMs version did not have a heat shield.
I am happy to see DDMWorks has come out with a CAI with a heat shield. That is the one I am leaning towards.
DDMWorks - LNF Air Intake System - AIS
I am no expert on the subject though.
