K&N power

[EX400rider]

will i be able to tell a difference with stock 400 but with K&N airfilter.

maybe but its definetly more noticeable withe a pipe and but please dont get a slipon aftermarket headers are so much better

[bwamos]

Aye,
K&N w/ "Full" Exhaust and rejet will give you a very noticable increase in power.

[jak1389]

if you just add a k&n you will probably only feel some throttle response. but the overall power i would say no.