if u use and prep a k&n properly you shouldnt have any problems... u need to make sure the ENTIRE filter is cover with oil and that u clean it often. in sandy/dusty conditions it probably needs to be cleaned every ride depending of course on how much you ride.

 

what i'm doing is using the pre-filter that comes on the stock polaris filter over the top of my K&N, fits perfectly, keep some of the larger stuff out......you have to clean the k&N's as well as any other filter on a regular basis.....

 

I to was using the factory cover over my K&N. BUT, one day while cleaning the factory pre-filter, (this may sound sick) I put my mouth up agianst the nylon pre-filter and sucked in hard. I found that it resisted air flow. I put it back together with just the K&N to test my theory and gained about 8mph on top end. No Joke. I have alot more power in all ranges.
"03" sp 600

 

After reading your message, I had to try....not experiencing the same thing here. It did feel like it draws better one way than the other....but is pretty much free flowing on mine....

 

I use the Outterwear's pre filter on mine, looks to be the same as the stock one that I keep as a spare.