There are several different systems available. A simple check on ebay will show various that all look fine. I am keen on replacing the Y pipe and the cat back for increased performance potential. However, I am very keen on being allowed onto race tracks, so am keen on the noise level not creeping up too much.
Does anyone have any experience on any of the individual manufacturers systems? Milltek seems to be the most popular, since it appears that both Litchfields and SVM use them, but I am ever on the look out for a cheaper alternative!