I replaced the sound deadener with foam filter on the hood, and noticed it wouldnt rev past 8000rpm @wot.Next day i removed the foam, and was hitting over 9000rpm.Weather was extremely cold @ -35c. The only thing different that happened was my sled was froze up in the morning,and had a lot of belt smoke before it freed up.Is it possible that the belt got wore enough to cause the significant amount of rpm increase. Wasnt running lean with no hood filter,as plugs looked good
sounding like your primary clutch needs cleaning and inspection.