The stock air filter just doesn't appear to make good seal to the box. I'm thinking of replacing it with the pro design adapter and uni filter.

If my quad is all stock and I just replace the filter will I have to rejet?

Thanks.

 

if you leave the air box lid on and the stock spark arrester in , no.
but why would you do that?

 

I've got sort of the same question. I put a K&N on my KFX and removed the spark arrestor. It rides just fine now, but if I take the air box lid off it bogs down way bad when I hit the gas. Should I take the cover off and have it re-jetted?? Will there be a power difference with it off?

 

if you remove the lid and the spark arrester ,yes you Will have to rejet, a 142.5 small main is most likely the jet you will need .
this jetting is for under 3000 ft.
yes it will give you more power