Guys, there is a huge difference with the "box" from Carnewal.
It keeps the valves open all the time, which the original setup, even with the sport button pressed, does not. Even with the sport button pressed, the valves operate according to the DME programming but since they open up more (and longer), you get the sportier sound vs. not pressing the sport button. With the little box from Carnewal, this process is eliminated, the valves stay open all the time, thus you have a louder sound than with the original setup, even if the sport button is pressed.
You actually need to install the box, try it, then go back to the original setup and you'll realize very fast how big the difference is. Especially on the Cab, the difference is huge.
So to actually hear the difference, I would recommend lowering both windows completely and of course opening the sunroof (Coupe).
As to the negative effects to the engine: I doubt that the slight changes in back pressure have any serious negative effect on the GTS engine. It would probably be different on a turbo engine. Of course torque is changed to some point (and you can actually feel it a little bit) but performance is still the same, I tried several 0-100 kph and 0-200 kph runs (GPS) and the time was 4.4 sec and 14.5 sec, so within original "specs" (both with Sport Plus active and without launch control).
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RC (Germany) - Rennteam Editor Porsche 997 Carrera GTS Cabriolet PDK, BMW X5M, BMW M3 Cab DKG, Mini Cooper S Countryman All4