The P4SS actually had the too long 3.7 differential. The 4.1 was extra money. But the sound was a beautiful thing. To be honest, after three years I sold the car because it was damn loud, especially because I had my P4SS changed to be a LHD. With that I was sitting on the same side as those STBs, which is much louder as a driver in a RHD car. I know because I was a passenger in my car sometimes. The bonnet acts as an intermediate acoustic damping device for RHD cars. Here is a video from 2012 near Bozen.
