Had it out for some riding yesterday. After about an hour's riding I pulled the plug and it was a touch on the lean side. Pull out the 144 and put in a 148. After another couple of hours I pulled it again. Looked much better but think I might go to a 150 on the next outing. As far as how it runs? Not sure I know how to answer. It feels much stronger on low end but I kept asking myself if it really is or do I just want it to be. I kept thinking it was like when you wash your car, it just runs better sort of thing. It is louder than stock but I don't think it ie too loud yet. It sounds so good and different from stock you just want to play with it all the time. I let a guy ride it and I rode behind him on his Griz and I could hardly hear it unless he got on it hard. And I did not have a helmut on. I am not sure how well the Rinny should run against a Griz. but in a quarter mile he was barely inching away from me. He had me about 2 bike lengths. I ran a Prairie 650 a couple of weeks ago and beat him by a couple of lengths once and we tied once. Overall, I think it really helped and I know if made it more fun to ride. Oh yeah, I got to pull the Griz out of a mud hole. Loved every minute of it, too.