RE: Oil Catch Can: Its Purpose.
the pcv is on top of the valve cover and releases oil that blows past the internals under high boost situations. all it does is release the oil to get it out of the engine. you could just run a tube down to the bottom of the motor and it would drain to the ground, but of course the epa doesn't like that, so they require a return hose which sends the oil back to the intake manifold where it is burned. this theoretically will reduce power since the oil takes the place of air that could be used for combustion. however, it primarily just gunks stuff up. therefore you put on an occ to separate the oil b4 it gets into the intake to prevent this problem.
like i said, if you wanted to, you could just run a tube to the bottom and drain it to the ground- dcx obviously can't design it that way due to legal reasons, and most of us either don't want to pollute or don't want oil all over the garage floor or bottom of the car.