a catch can is just a good piece to have all the time. all it will do is catch loose blow by oil instead of having it head into your intake stream. i've always ran one but am disappointed every time i see people selling them for $100++++++. they have them on eBay, pretty nifty looking and they have a nice looking 'mazdaspeed' cap on them too. or you could just do what i've always done, but a small clear fuel filter from autozone and just run it in line of the valve cover to intake line. allows the breathing and catches all the oil, you just gotta watch it and replace it when it starts getting clogged up. fuel filter $2, catch can from name brand $100+ easy, catch can from ebay that does the SAME exact concept, $30-40. you choose i guess.