Ive just decatted my classic as well, at first i replaced just the center, diddnt really make much difference, and after having greif with my flame kit i dun the downpipe as well, i now have straight through from turbo back, with the exeption of a resonator in the center section, well worth the fun i had fitting it with limited tooling, sounds great, more pops and bangs and the flame kit makes a bit of wee come out, when its switched on..( thanks to some helpfull peeps on here). only takes an hour to fit a cat for the mot, so go for it BLUE,