I do because it is chrome, and now because I went to put on my stock cap, and when I'd shut off the car it would hiss (like relieving pressure) for a long time.
Needless to say I just stuck the breather back on. No problems anymore...lol
They will reduce the amount of buildup in your intake ( but it takes a long time to build up anything worht worrying about. These filters will leave an oil residue on your engine becasue the fumes that come out of them contain the oil. It is up to you if you want to use them. You win some, you lose some. IMO