Ignore Souk. It's easy to outrun the competition when you've got a fresh rebuild, 964 cams and tires wider than my house in the rear.
I've run the elbow with my premuffler (Fabspeed) and i'll agree it's ridickerousry loud. But I can say with certainty that the sound is better with a premuffler that has an expansion chamber like the Fabspeed or Dansk. The straight-through cat replacement pipe is what you hear in my video of Swamp Rat Stefan passing me.
http://www.youtube.com/watch?v=9MNWPJHqPZw
His car is raucous and on the cusp of sounding track illegal. At one of our events he was tagged at 103dB and max is 104. I don't really get a kick out of the elbow. But it is pretty funny when i'm lazy and don't feel like putting a muffler back on after track events- leaving the toll booths at full throttle gives a new meaning to the term "loud pedal."
All that BS being said, I think there is a definite gain by replacing the stock muffler. Throttle response seems a bit better and the car seems to pull better at high rpms. But by no means do I endorse the elbow for street use- or even track use for that matter. I agree overly-loud cars at the track are bothersome. Funny thing is, my car isn't one of them even with the elbow. Some of the dedicated track cars with high strung engines are unbearable to listen to as a spectator.