I'm sold on the breathers. They look cool and appear to be functional.

I'm looking for a cast(Mercruiser) valve cover and these look like they would work great on it. Breathers for 20 bucks are more than reasonably priced.

Are 2 breathers needed, o were two installed for the sake of symmetry in the appearance?

If at first you don't succeed,
then read the directions and try again.