Believe me, you havent had BAD blowby until the breather going to the intake is so oil laden the engine takes off.   This will make a terrible noise and completely obscure the road behind you with blue smoke.
Getting stopped is quite exciting !!
I have never owned a diesel Vanagon but for a while I had a Rabbit pick-up with the same engine.    Yes, it took new rings to solve the problem.

Steve Cotsford