Grant:
Adam2S:

Shmee150 has added a full IPE Innotech Performance Exhaust system, including headers, 200-cell high flow cats and Valvetronic muffler.

His youtube review of it is worth a watch if you are interesting in changing from the stock exhaust : https://www.youtube.com/watch?v=AQqmymJQshc

Though supposedly the IPE system has been plagued with some quality issues and some people removed them very quickly (don't know the details).  I also would be rather dubious of any power gains from just an exhaust (though almost every manufacturer makes such claims), if it does not come with intake and tuning mods too. 

Personally, the whole engine (and its electronics) is something I wouldn't mess with while in the warranty period.

Having seen and heard the 991 GT3 with the IPE exhaust I could imagine that one reason for dropping it would be the noise. I heard it at a track day and it is loud. It is also the only time I have heard a street GT3 which sounded more like a racecar at WOT down the straight. Personally I really liked the sound.