Since I owned a shop in central California in the mid-1970's I installed dozens, if not hundreds of those PCV retro-fit kits. At that time the California Air Resources Board (Yep- - - -CARB) was operating roadside emissions testing- - - - -pulling over a bunch of cars for a visual under hood inspection and an exhaust emission test, there was a huge amount of pressure for compliance. The fines were very steep for running an unmodified vehicle or one that had a smoky exhaust. Later the SMOG test was only required when a vehicle changed ownership, but a visibly smoky tailpipe still got the driver ticketed.
Jerry