I'm chasing an issue with high crankcase pressure, it's actually a 2005 Transporter T5 with the AXA engine but I believe it's essentially the same motor as a 2.0L Mk4 Golf and early 2000s Beetle.
It has very high crankcase pressure, enough to pop the dipstick tube out and you can feel it quite strongly if you pull the oil cap off.
I've made sure all the hoses etc are clean. I don't believe these have a PCV valve.

It has high compression across all 4 cylinders and seems to pass a leakdown test too.

Any suggestions would be welcomed.