Mark -- what original part(s) do these replace and do you have any installed (with photos of the ballasts mounted) in a 2008 CTS? I might consider it, but I am not for guesswork.
Also, what is the difference between these and some PIAA replacement bulbs for foglights?
http://www.xtremewhite.com/ORD-Light...35-1-1-1-1.cfm
Thanks in advance.