I have a 2bro's CF pipe on the fz1 - would of left the areap had I had the means to make a proper midpipe.
When I first installed it, I thought it was too loud, and I would get headaches on long rides. I ordered and installed the p1x tip, which muffled it considerably. One day, on a whim, I pulled the tip out and rode the bike for several long trips that way. Eventually, I thought it sounded better with the tip out, and it didn't bother me as much on long trips, esp when I have the medium height touring screen on (vs the full height vstream fall/spring screen). I still have the p1x tip, but doubt i'll be using it any time soon.