You can say the same thing about the first EGR valves too. It's only function was to re-burn exhaust gases to keep emissions down. But the modern EGR systems on computer controlled engines actually lower in-cylinder temperatures, which can improve performance and gas mileage. Both the EGR and PCV started out being considered emissions "crap", but were later found (or developed) to be beneficial to the engine.

 

I have a friend that has a 74 camaro 350 and he has pcv on one side and just open hole on the other valve cover, so he bought one of those round breathers to put in the hole and man it starts whislting. If you just put your finger over the hole its got crazy vacuum, it will suck the skin on your finger hard then it starts to die. I told him to pull the pcv valve out to see how much vacuum is coming from it and man thats where its coming from. I have never seen that much vacuum coming from one of those I thought it was always just a slight amount of pressure, anybody know why it would do this?? I know it hooks to the carb base,but why so much vac??