Source for new 273 commando valve cover breathers???

I dont know the answer for that one. I've heard that the early valve was placed on top of a beather cap because the valve covers didn't have baffles in them. I dont know if thats so either.
Before PVC the crankcase inhaled and exhaled under the hood. The exhale was more a oily vapor that air polution. In fact , burning that oily vapor polutes the air as much or more. The main advantage we got from PCV routing is keeping the engine bay cleaner.