After the problems with the new Longlife (Cardiff) exhaust - have they ever built an exhaust for a supercharged car before???? If my experience is anything to go by then they haven't. It was so loud that you needed ear defenders to drive it when the supercharger cut in. There was a loud pulsing noise when under load at 2500rpm to 3000rpm especially going up hills. Longlife basically said that they couldn't do anything about it.
I did some research (I know now that I should have done it before buying the Longlife) and came up with Stealth Systems in Southampton. I made a phone call and booked the car in. They built me a system with 2.5" pipe work, high performance cat, centre box and back box with 2.5" outwardly rolled tailpipe. Stealth not only make exhaust systems but they do manifolds and fit superchargers to normally aspirated cars too. Their experience paid off - the exhaust is quieter and although the pulsing is still evident it's nowhere near as bad as it was.