Had my car in for a service before the warranty ran out and decided to give myself an early birthday present. Installed the GMG exhaust bypass and it sounds better than I could ever of dreamed of. It sounds like a lion roaring when you fire it up. Absolutely love it! Porsche should just make that sound standard...

 

Do you have a sound clip?

 

Another after market exhaust was on my car when I bought it. It had steel mounting brackets attached to the Stainless Steel pipes, these were very rusty in only a year or so.
Bought the GMG and it is well engineered and sounds like a GT-3 should. Have you listened to it in sports mode? You'll love it.
There are several sound clips on the GMG site.

 

i bet you wish you would not have waited so long......

 

I pretty much drive in sport mode all of the time just because the sound makes my blood stir and it sounds like a symphony!