As with all aftermarket companies they do inflate hp no. a little but yes they do give you more hp on the 700 but not as much on smaller sleds. But the trick is to get more hp to the ground since you loose 25 to 30% of you hp through the clutches chain case and track you will gain more by making these areas more efficeint through clutching gearing etc,so it does not do anygood to add power to the motor unless the rest is up to the task.I suggest you spend so time on the chassis making sure everything is true and square and all bearings have no bind or drag in them,this includes jackshaft,driveshaft,is the suspension perfectly square ie rails etc and is it perfectly square in the tunnel is the track perfectly aligned and the skis aligned to the track (use a long straight edge run it along the track to the front of the sled and measure ski alignment to the straight edge and not the other ski) All things that I mentioned are cheap but they take wrench time and the performance increase is more satisfieing since you did it your self also you will learn more about your machine in the process.
.........SNORAT........