I have a September 07 4.8M sport, it has the standard oval tail pipe at each side which I would like to replace with twins each side, I have seen a mod for the Diesel car but not the 4.8 so I assume the back box would need to be replaced on the 4.8 which might make this an expensive mod as the tail pipe is formed onto each side of the box, there is no removeable section, anyone tried/thought of this ?