My 12s is the same way. I don't hear clanking or anything like that but a do hear a lot of whistling and general machine noises (great description huh) coming from down there. I had an R6 and heard nothing but engine noise from that thing until I got a new pipe. Stock exhausts quiet the bike down so much they always seem to be choking. After a pipe is fitted all you hear is what your supposed to hear....the exhaust note. My Jardine should be in next week. That should fix the engine noise problem.