I have a 2007 R6s. It has a yoshimura pipe, and a power commander. I bought it brand new and I now have 10,500 miles on it. Since installing the yoshimura pipe a few months ago I noticed the sound difference. The sound is awesome when you get on it, but cruising it the pipe pops a lot and sounds almost like a boat exhaust under water. So I got a power commander and had a custom MAP installed. The map made it run a little better, but I was expecting much better out of it. The bike way dynotuned, but the pop of the pipe is still around. I was told yoshimura just has that sound, I was also told to get a spark arrestor to make it better, but what I started to think about was the spark plugs. I have never changed them yet and your suppose to change them at 8000 miles, I now have 10,500. Will changing my spark plugs make any difference at all, or should I just save my money and wait a little longer before changing the plugs? Also when I'm out riding I notice somedays my bike is running really good and idles so clean, and other days the idle jumps around a little bit and runs less responsive.