I had it on my 2010 RZR S with the fuel controller and noticed a difference. I was able to get up to top speed just a little faster than all my buddies, even with all my accessories, spare tire and J-Strong. It was fun to wind them out on a long road. The only negative was how loud it was. I couldnt hear my music over the damn exhaust. I have an XP now and wont put another aftermarket on it.....too much noise for so little gain.