Where would I put a breather on an 02 GV?

I've seen some pics of 02 GV's with breathers, but where do they go?

What do you mean by breather?

I mean a breather filter, the one that looks like a mini air filter.

http://www.autozone.com/images/products/mrg/mrg2043003.jpg

Is there any place (or places) to put one of these? What exactly does it do?