Is this what I use to catch the oil from the PCV?

Roland69 said:
do they go inline kinda like an inline filter (but not a filter just an oil catcher) and why would you need one
Yep, it just goes in-series. Guys have used a filter (like a clear fuel filter) but it can require periodic cleaning (even the element in my separator kept clogging, so I ditched the element).

It helps keep blow-by out of the intake, which keeps things cleaner and arguably helps ward off related-detonation. I think a lot of us do it just to do it.