World's first Pagani Huayra with custom exhaust!!

I have filmed the world's first decent sounding Pagani Huayra during the 6RDS event at Monza circuit. As you can see/hear this particular one was fitted with a mysterious custom exhaust system never seen before on a Huayra, and believe me, it sounded incredibly good compared to the stock one! >> http://www.youtube.com/watch?v=zTu94kyWtfQ