vacumed pcv?---question

The reason this style of breather is used in racing is that there is little vacuum in the intake manifold under WOT conditions to evacuate the crankcase when it needs it the most.

Tranversely, this system pretty much does nothing under street conditions where a positive crankcase ventilation system works at peak efficiency.

The third option is a belt driven vacuum pump that pulls vacuum under all conditions. Of course a special made valve cover set up is needed for this and it's not cheap.