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Originally Posted by 2000SoCalBoxsterS
Patrick, one thing you have to consider before being to hard on the Fabspeed guys is that the system may not be drone/resonance free without the $2,265 Header/Sport Cats. The exhaust flow, pressure, ... is diferent without them and that's why you have the drone. When Fabspeed tuned the system and tunes out the drone they did it using their complete system.
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First off I know little to nothing about exhaust design and engineering, but having worked for Harman for a decade and competing successfully in car audio I do know a little about audio. The pulses of exhaust pressure produce long wave length sound waves which we know as the exhaust note. In a front engine car you've got a lot of exhaust piping going to the back in which these long waves can be canceled out or dissipated. Then putting on a free flowing muffler is no problem. In the Boxsters though we have a relatively short run of exhaust piping due to the mid engine layout, so more emphasis has to be put on the muffler itself to cancel out any undesirable sound waves. From the cross sections I've seen of the stock muffler that's EXACTLY what it does. It's designed the same as an acoustic band-pass box.
I think that if you then replace the stock muffler with a straight-through, free flowing design muffler you're going to have resonance issues, no matter what you do with headers or cats. Changing the headers or cats will affect your flow, but not the cancellation of annoying resonances. I believe the key to that is proper design of the muffler can itself.
Just my opinion...