Correct me if I'm wrong, but I thought the PVC hose needed vacuum to overcome the inherent ball valve inside it. My understanding is that it needs to be connected to the base of the carb or on the intake. If you have a regular breather without a pvc, then it can be routed to the oval breather. I had a simular problem with
oil being forced from the dipstick and it was caused by (1) baffled grommets on the valve cover breathers (2) lack of a pvc.