I have seen a few minis with crankcase breathers. I have like 5 small breather filters laying around and I'm interested in doing it myself. Where does one connect a filter and what is the benefit if any?

 

On these people tend to use a catch tank, the purpose if to keep oil vapour out of the intercooler and combustion process, the tanks vary, so just find a neat one that requires no holes, and has a sight tube and easy drain out.