Apparently Europipe has a Stainless GT3 Exhaust
Apparently Europipe has a Stainless Steel Sport Exhausts for the GT3, dyno results +12hp which seems a little suspect to get that much out of a system that has already been heavily tuned by Porsche Motorsports. Also saves 8lbs.
Heavily debated on Rennlist along with the Fabspeed GT3 exhaust+headers which have an even more outrageous claimed increase.