I can't accurately comment on another system only my own. If the DC sports manifold bolts directly to the spoon cat back and there isn't a section to unbolt were the cat should be then the manifold would have to be cut and welded to take the cat. If it does come with a section you can remove then I couldn't say if the flanges would mate or the Piper sport cat would be of the right length to fill the gap. You could get the Piper cat and then get extra flanges from piper so your other sections can be altered to match it... if you know a good exhaust shop or just get the piper manifold as well as sell your DC one. As regards to gains, a decat pipe will be of less restriction than any kind of cat so you would lose a few hp by fitting one. The point of the sport cat is that it is less restrictive than a normal cat, nearly as good as a decat, but doesn't require messing about and is 'legal' come MOT time. I say 'legal'... it will pass the emmisions tests but they have been illegal (for a garage) to fit a sport cat since 2010 as they don't comply with EU standards. Not all garages know this fact, as I found out, so unless your good at welding you'll have to find one that isn't bothered. It's also illegal to have a car with a decat but seeing as you have one your probably not bothered about that :lol: