I have my airbox lid off an dmy pipe is uncorked. Other than that my bike is stock. New years was my first trip out and I didn't lose to many banshees at buttercup or at test hill at gordons. I beat stock(appeared to be, with the exception of pipes), by 3 or 4 bikes. But I would lose by a couple bikes to modded banshees and full out drag banshees. I'm a big guy(6'2" 230), but my brother who weighs 150 lbs didn't lose on my bike at all. He beat a kt400 shee by about 6 bikes. And my brother who only weighs 105 pounds beat a full out drag banshee with a cr500 motor in it. The yfz's are quick. That is for sure.