see there my friends here have tons of great info. i remember when thy started using PCV valves. the only smog part my dad thought was good. cause the engine had a LOT less dirt going in the crankcase.
That's what my instructor told us at tech college back in the 70s. A lot of the guys in the class were racers and the teacher was adamant that if we chose to get rid of the rest of the smog equipment to increase power we'd see gains. But if we got rid of the PCV setups we'd be shooting ourselves in the foot.