the little air breathers you can put on in place of the tube going back to your intake, what is it for, is it just a waste of money??

It's mainly so no oil get's back into your intake system (some what a problem in the 4g63, gumming up intercooler and all pipes in it's way). We seen to be ok non-turbo. But when running a turbo 420A I recommend getting a catch can for some extra oil that might come out. If you run just a breather filter on a boosted 420A I can almost guarantee a mess of oil in your engine bay. It just keeps the inside of the intake manifold a bit cleaner. I would not consider it a "performance" mod.

Oops. Forgot to mention it's main reason the factory installs it: Emissions.