I guess Porsche Motorsport is the performance division. Customers can get anything from Porsche Motorsport, unfortunately not for street use.
Ron is right, Exclusive department is actually Porsche's "real" AMG division but I have to admit that AMG offers much more technical stuff for customers than Exclusive department. Funny thing is: most of this AMG technical stuff isn't officially available in the US or even in Germany through official Mercedes dealers. You have to contact them directly.
Another thing which makes me a little bit concerned:
a guy at my dealer had the GT2 front bumper and rear wing installed on his 996 Turbo. A technical rep from Porsche saw this car and put it on their "black list" (VIN is "blocked" for specific warranty work in the Porsche IPAS system).
Now somebody went to a track event last week and met a guy with another 996 Turbo with GT2 front and rear wing. This guy claimed (and proved it) that he had the GT2 front/rear wing installed by Exclusive department on his new car (after production finished, they took his car and brought it to Exclusive to modify it).
I heard from many sources that some things are possible and some not but shouldn't it be more like "all customers are the same?". I'm not sure if this story is true but when I went to Exclusive and asked about a X50 retrofit, I was told that it is possible but I need a new gearbox. And a few days ago I actually heard of somebody who did this.
But officially ... no X50 retrofit, no GT2 front/rear wing.
Strange.