Well, I started out with a K&N drop in filter. It worked alright, but no noticeable difference. Then I upgraded to the FIPK which yielded noticeable improvements, but after three days my car is now in the shop waiting for a new air flow meter. So I've ripped out the FIPK and don't want to screw myself over by putting in another wet K&N filter. What's everyone's opinions with TRD air filters? I talked to my mechanic (toyota certified tech) and he told me to just get the stock Toyota filter. Any thoughts?