In 2015 I bought Steve's Shoodaben Engineering flash and loved it. Although it was a lot less refined than the new flashes he builds it was a huge improvement. Then along came the Evolution flash and ...again it was a nice upgrade that I added in 2017 and I went crazy with the improved power and better fuel mileage. Fast forward to two 3 weeks ago and I had some email conversations with Steve and I was considering the Mountain Runner upgrade or hopefully the Mountain Runner Premium. Turns out I don't have enough access to the 92+ octane fuel here in Utah since the best I can get is 91 and sometimes even 89....Mountain Runner Premium wasn't going to work for me. Then I decided on the Mountain Runner 89. Steve said that it really didn't change anything over 10% throttle and I wondered if it would really be worth it or if I would even notice it. For me it was a huge improvement for my riding style and very noticeable in the 700 miles I have put on it so far. Better and smoother off on throttle response and very smooth and improved decel especially on downhill and over 4500 rpm. I also realized that I do 90% of my riding between 3,400 rpm and 4,500 rpm and that is where the smoothness really counts for shifting and overall feel....easily withing that 10%. I do roll on throttle to 5,500+ rpm on every opportunity like on ramps and open roads and the extra decel really helps on my reading style. If you are considering this upgrade I give it a big thumbs up. Smooth as butter and so worth it!!