i´ve compared all the combinations of air filters, k&n,taking off plastic cover with washers, etc... it seems like these all ruin the low rpm drivability. i´ve went back to the stock air filter and cover, and all around performance is much smoother. i did notice a little more pep at higher rpm, but it wasn´t worth the trade-off. seems like treating the symptom rather than finding the cure. these are very fun bikes when running properly. just got mine out today. good luck!