Hi Liam,
Notice you are potentially going for the same as me (race backbox only)? Is the rest of your system standard (mine is) and I don't suppose you found a video of just the race backbox?
My thoughts were changing the exhausts on these cars for power is essentially a waste of money really and can introduce issues with the mapping/flat spots. So I thought just chaning the backbox can not do any harm other than save a few kg's and improve the noise - which I thought the Sport backbox might be a bit quiet when I am keeping both cats and centre box etc... I am however really hoping it wont drone etc as I use my car for motorway driving alot, but I don't think the backbox is normally the reason for drones?
Cheers,