I gutted mine, shes a zx6r 06 636, little different to your 07, i used a screwdriver and hammer to knock out the cats inards, then hoovered all crap left over, started her up and blew anytiny bits out, just make sure you use a mask... She sounded a little louder, but may have been me ? ? when i took off from a set of lights rather rapidly front came up, shifted up and she came up in 2nd just of throttle, never really done that b4, so may have done her some good breathing wise or little bump in road made her come up at that exact moment i cracked throttle open into 2nd , she pops a little when i shut off at high rpm which always sounds good, only every so often though..im very pleased with how she runs..got Power commander , and Arata pipe on with a k&n also, so gutting cat was next thing to do..good luck matey let us know how it goes..:bigthumb: :bigthumb: