thats the one as you look at the engine on the r/h side .. on the inside of the block there should be a small black plastic plate that just clips into place ,
i only found out about this on the cvh as it happened to me.

Brasso
if the return pipe is lower than the oil level then oil will travel up the pipe on cornering..

it sounds like you need to have some form of one way valve on the return pipe as i think its not the fact your breather that has the problem but the oil is being forced back up the return pipe and the only other ways it can go are back into the head or out of the pipe into the catch tank