Its only venting the crank case and the valve cover. doesn’t see any intake vac or boost pressures. only pos or neg pressures inside the motor.
on the last build for the jetta, I sent the valve cover vent tube off, T’d into the crank case one and slapped a filter on the end to piss out oily vapor under the hood. :tongue Ran just peachy. if it recirculated, I assume it would need a check valve so under boost it didn’t cause a boost leak or pressurize the valve cover and crank case.