From my personal experience:
I originally blocked off the PCV valve had a vented catch can with a line coming off of each valve cover. I never had the blowby issues you are having but I did notice that my oil got dirty petty quick with the catch can. Also, if there is no way to pull the combustion gases out of the crankcase, like a proper PCV system does, these gases settle onto internal engine parts and into the oil. This will cause engine parts to corrode over time. Like this:
I installed a modified PCV system on my draw thru turbo car. I used a Turbo Coupe PCV valve which has a check that is not supposed to allow boost into the crankcase. In testing it worked properly about 50% of the time. I still used it (will probably go back and gut this valve) and ran a 3/8" line off of it to an oil seperator like this one: JEGS Performance Products 52205, JEGS Air Oil Separator | JEGS Performance Products
. From the other side of the seperator the line goes to this check valve: McMaster-Carr
which is very well built and will not let boost pressure back into the crankcase. From there it splits into two 3/8" lines that run to the intake.
To pull fresh metered air into the crankcase, I used the factory nipple off of the passenger side valve cover and ran a line into the piping after the mass air meter. I installed an inline fuel filter like this one: http://www.autozone.com/filters-and-...er/246927_0_0/
just in case to keep anything out of the intake tract. The filter is hidden under the front fender because it would look terrible if not.
I then installed this in place of my sealed factory oil cap: http://www.c-f-m.com/performancepart...idproduct=3206
. This oil cap/breather has an internal check ball and is baffled. It seals off under vacuum and does not allow unmetered air into the system. When in boost it opens and vents any crankcase pressure. It is a high quality piece and works well.
I now have a closed PCV system on my boosted car that works like factory. This setup works perfectly on my car since it is draw thru. On a blow thru system the metered fresh air would have to come from a different (non boosted) source like the inlet of the turbo/supercharger.