Regarding the PCV, here's an answer I got from a Bauer tech.
Routing the PCV back to the 1st stage does a few things:
1. It eliminates oily residue from building up in your compressor room as the atmosphere vent will have some minor amount of oil residue being carried out with the air.
2. It uses this minimal amount of oil to provide "top lube" to the #1 piston and cylinder.
3. It helps the compressor breath better by pumping air into the first stage so that cylinder isn't having to pull in all the required air for compression on its own. Less work should mean longer life.
I know from flying jets that some of our fuel systems use a thing called "Motive Flow" to provide an assist to moving the the fuel. Basically, your pump shoots a high volume of the fluid into a collector pipe which creates a low pressure area behind it and causes increased flow into the fuel system. This allows the use of a smaller pump to move the same volume of fluid that a larger pump previously moved. In airplanes, it saves weight which equates to fuel savings.
If you've ever seen this fifth grade science experiment, you'll understand. Take a ten foot long tube of a light weight nylon cloth with one end sewn shut. Have two assistants hold each end. If you put your mouth up to the open end like your filling a balloon, you can not blow hard enough to fill the tube with air. But, if you back up about a foot with the assitant holding the tube open and then blow: you can fill the tube with two or three breaths. Because your blowing into the tube creates a low pressure zone going into the tube and ambient air pressure is higher; it will seek to equalize the low pressure and fill the tube until the pressures are equalized.
