The road draft tube only pushes out blow by gases - it can't suck in air. Pressure is always positive inside the crankcase without PCV.
Using stainless wool is mostly to prevent splashing oil to directly escape through the draft tube when the pressure increases.
Also the tube end is cut at an angle on purpose away from the driving direction.
Starting around 30 mph the crankcase gases get sucked out by the lower pressure air rushing by the angled opening.
The faster the speed the more gases get sucked out - exactly the opposite from a PCV system :rolleyes:
