at idle/vacuum air will draw from the the driver side breather port through the pcv (one way valve) into the intake manifold.
Any time when you start making boost, the pcv will block and no air will draw into the intake manifold. Air is sucking through the passenger side breather to the the rear turbo intake.
I think in a idle/vacuum case the pcv side has higher pressure drawing in, and the turbo side isn't doing much. Plumb your can inline with the turbo side and reconnect your pcv like stock. Or plumb both sides up into one can, or run two cans alternatively. The turbo side will pick up all the oily fumes on boost. The pcv side only picks up oily fumes during vacuum situation.
here is the right way to plumb your can, every other way is probably incorrect
http://www.skylinesaustralia.com/forums/topic/40402-greddy-oil-catch-can/page__st__60__p__1179419#entry1179419