Hello mate i dont personaly have one on my car but a friend of mine does on his astra coupe 2.2 and it does sound wikid on his car gives a brilliant tone only down side was it whistled as he was hitting high revs around 5000rpm it would make a loud whistle but he took the back box of and the was a flange in the exhaust witch looked like it was the cause he simply cut it out and whistle gone .... i dont think it is all cars it whistles on his was a 1 off but they make a great noise
im sure i could get a video up on you tube or something if you are realy intrested
