They say the the threshhold of butt dyno is about 5hp. That means you could barely sense the 5hp increase. Any less of an increase and your butt could not feel it. The true benefit of dyno tuning is normally throttle response. That you will feel, though it may not make signifigant #'s on the dyno. In general a spocket change will show up on a dyno curve as tourqe and as such will feel like throttle response. It will not improve Hp #'s. Personally I gave up 8 HP on my track bike for 5-8 ft/lbs of torque from 4000-10,000 RPM. I spent lots of time researching the 04-05 R1's to make sure that I built my motor for tourqe, happy to give up peak HP for across the range Tourqe. My engine guy was amzed with the changes I made. He originaly dynoed my bike at 161HP with slip on's and a commander. I brought it back after I moded a bunch of stuff and it made 153HP but the tourqe curve looks like a v-twin from a bike that was notorious for weak tourqe.
Point being, worry about the #'s below the curve, not the peaks. Remember, on the track your bike is only making peak power at shift points, the other 95% of the time you are worried about below the curve. Just ask the poor guys that use to have to ride 2 stokes to championships. The good ones were always either on the podium or on the ground.
