Thanks for all advice guys. I feel that I own you the result :-).
Couple of weeks ago I was down racing at Tor Poznan (Polandīs only race track and actually a former F1-track), for three days, whit some 100 people mainly from Sweden, but also from Denmark, Norway, Russia etc. (http://www.granturismoevents.com/gra...-polonia-2012/
There was another guy from Stockholm down there with his M3 GTS (one of two sold GTS's in Sweden), and as this guy had a BMW M Performance exhaust system in Inconel laying in his basement (for no use) from an old m3 "lightweight build", I was offered a quick deal. As the price on this barely used BMW original part was decent, and as he claimed the sound was identical to his original BMW GTS system (which I thought was perfectly raw) , it was a deal. I was invited to come along for a few laps in the GTS and I can tell you, it is an extreme BMW, that one (however, more of that another time) :-).
I can live with the fact that the system doesn't add any extra HP, when knowing it shreds about 10 kg off the total weight, is built in a material common within F1, and has a sound that is just incredible nice. Ok. It doesn't sound as a jet flight, but on the other hands, no drone inside, whatsoever is created. To sum up - I am really satisfied!
Over and out.