Actually, Apexi makes the best filter. Here is a comparison:

Car Filter Review

Only had my K&N's in for about a week, no problems so far. I don't know if it's just in my head or if I actually got gains, but it feels like I have slightly better throttle response and power. I think the engine sound/exhaust sound is a bit louder too (which I like). The stock filters were fairly dirty anyways, so I'm sure the engine is breathing better in any event.

Guys I just got these last week. I did notice a slight bit of throttle response. I bought them from StreetSideAuto.com for $39.57 a piece. With shipping they were $89.09. If you don't already have these, buy them.:tup:

I haven't noticed anything with my drop-in's :ugh2:

I got my set for ~$75.00 from AAP. They had a nice promo code going on at the time

I know this is quite an old thread, but I came across this video and it kinda puts any "do they do anything" debate to rest:

https://www.youtube.com/watch?v=uf2Do9dQzn4