alright, so if i switch to a K&N filter do i take the silencer out? i've read this a couple places. or is the K&N larger than the stock housing? also..., you mentioned metal CAIs, which i've heard of before and it makes sense seeing as how the metal would absorb the heat, then transfer it to the air being transported. what i'd like to know is how much HP a plastic tubing CAI would free up.