Dr_Jekyll & Mr_Hyde Estate Project

[dr_jekyll]

If the breather is only an issue when attached to the inlet then you have a restriction upstream that's causing vacuum to draw through more oil from the head. It'd have to be a pretty major restriction to draw that much oil though, is your filter clogged solid?

Oil filter?
Ive had problems with crankcase brether before but from past experience i need another pipe on hand as they tend to just brittle