Recently installed the Yosh RS-3 Stainless Steel bolt on. Paid $239 from my dealer. (Scott Powersports, Coopersburg, PA 610-282-4800, ask for Matt). I agree with the comments that most bolt ons look a bit ugly due to the Kawi flange used, but the pros to the slips on are as follows:
1. Easy to remove if needed. Warranty problems with motor...put the stock back on.
2. You loose no low end and gain about 5 hp on top. Most full systems loose a bit on the low end, have stumble problems, jetting concerns and gain 10-15 hp on top (above 8,000 rpms). I dont care who you are, and unless you are riding daily on a track, I dont see anyone exiting street turns on the ZX12s above 8,000 rpms all too frequently. If you tell me you are, I'm calling you a liar right here. I'll give up a couple top end horsepower and take the even low end, pratical street midrange grunt anytime.
3. A bit more crispness in the throttle response over stock.
The Yosh Zyclone is a bit quiet, and IMO, the Yosh Race is a bit too loud. It is not a quiet can. I would consider it just as loud as fully Muzzy, if not louder (my experience). I have heard, not experienced, that the Race is quieter than a D&D.
The Yosh fit is good, except the can does come within about 1/4 -3/8-inch of touching the underside of the stock turn signal.
Would I do it again....not sure. I like stealthy riding, but was looking for a bit crisper throttle response, which I did recieve. It does sound good when hard on the gas, but maybe a bit too loud for my aging years.