I had one. Don’t waste your money. The worst setup I’ve ever had on my car. The resonance is unbearable. It was so bad I took it off and put the stock muffler back on. I have a couple videos on youtube of the sound.
There is nothing inside those “mufflers”. The test pipes are NOT mandrel bent and about all they’re good for is using them as a template to fab your own pipes. The people who run that company are a joke also. I sold the whole setup I had for $450.
The first and third are my videos, the yellow Box.
http://www.youtube.com/results?search_query=boxster+stebro&aq=f