stainless steel exhaust and a de-cat pipe is a length of exhaust pipe that fits where your cat is thus replacing itl, the cat is very restictive and also acts as a silencer you take it off it sounds a LOT BETTER TOO.
august 1992 on i think you have to have a cat on your car but you can still replace it with a de-cat if after this date, just stick a cat on for the MOT .
i have a mk5 k-reg rs2000 with a ss exhaust and de-cat and it sounds the bollocks
cheeRS gary
AKA shrek