How much more H.P. and how big a difference is there from stock A.F. to K and N A.F? Anyone know??

 

The big difference comes with the lid removal or complete airbox removal. The k&N itself will yield a small performance increase.

Just read your other post. You are ready to challenge any yfz and you still are running the stock airfilter???

 

I was just jokin, thats funny I just ride for fun.