You should send a PM to Houston_C4S and ask him about this exhaust mod.
Mark put something very similar on his 07BoxsterS and it didn't give him any better sound nor did it give him any extra HP. In fact, it made his car sound like it was cutting a SBD fart on deceleration at the track coming off the straightaway. I heard this sound personally (ffffffffffffftt!) and teased him
relentlessly for wasting $450 and creating the world's first gay farting Porsche.
Mark said he looked at the Velocity Dream web site page you listed above and said it was nearly identical to what he put on and took off of his car. He replaced his exhaust system with something that is nice and loud and only has a little cabin resonance from what he tells me.
PM him for details. It was a lot more money than the Dream mod though. There's just no way to make our cars louder with little to no cabin resonance for under a couple of grand. Most solutions are in the $4-5k range.
