I've been looking into this a bit. How effective is this supposed to be at preventing the carbon buildup issue on the top of the lifters?
The conclusion that most people agree with is it does little to no impact. But, and there's a big but, anything a catch can would catch would get burned during combustion. This isn't good for your cat, this isn't good for your engine, and it's just not good for the overall health of your car.
Whether or not it does help carbon build up, it makes me happy knowing that my engine will run as efficiently as possible.
And... because screw the PCV system.