Without opening up the top end (flowed heads, cams, ported manifold, etc) I'm not entirely sure how much you'd gain with a long tube header. They are obviously much longer then the factory equipment and they require a replacement mid pipe/cat. You can either buy their kit or have one fabricated. Personally, I'd just buy theirs cuz you know it fits their gear. It shouldnt have any affect on your catback system so long as the exhaust is in the same location as factory and it pretty much has to be (not to many other places to route it).