Have a read of this, from another forum - may help
I have a 1995 993 Cabriolet. The previous owner had a motor sound package installed after taking delivery of the car. I was told that the motor sound package consisted of an air box and chrome tips. I was surfing the web and stumbled on the below website which states that when the motor sound package is ordered during build they use motor sound mufflers. Have you ever seen these mufflers? Will they increase HP or is it just for sound? Is this a Porsche OEM part? Where they used only on Euro models? The below was the desciption(with picture) of the mufflers.
The website is
www.carnewal.com
P93 Motor Sound Mufflers
These are the mufflers that come on the car when equipped with the Motor Sound option.They are more free flowing than the normal mufflers.For a P93 cars except Turbo
You are correct, the M159 Motorsound package also included the Motorsound mufflers. That is why it cost as much as it did. Yes this was partly a US vs Euro issue, and it was a short story you got with your car from the seller. He may not have known. Officially it was just for sound, but I swear they make a little bit more power. Maybe it's just psychological. Anyway since no more power was claimed, the muffler change was not considered essential by the people spending the money to add it afterward, whereas the rest of the change was quick, easy & cheap.
You can double check with Gert Carnewal, but I believe what he is offering are the Porsche OEM parts. TechArt also had a similar offering, theirs were not Porsche OEM, they were developed & tuned by TechArt engineers, and then they were manufactured for TechArt by the same OEM (Bischoff) that Porsche had used. So those looked factory, and sounded like Motorsound, but actually made and felt like the claimed 10 hp increase. Those were more expensive obviously.
The M159 Motorsound option was only offered in the US & Canada as far as I see on the PET CD (Porsche ErsatzTeile = Replacement Parts CD). There were actually two versions; a Bischoff version, and a Gillet version. Then there was another muffler version for the Euro Carrera RS, though it was not listed as M159 or any other option, it was simply part of the G64.20 RS engine.
Joel Reiser - PCA WebSite - 2/2/2003
