EGR will NOT add pressure to the crankcase. Turn the engine on and when warm, remove the dipstick. At idle, a small strip of paper placed over the dipstick opening will probably be pushed away, indicating positive pressure.
Remove the vacuum tree at the throttle body and inspect it for dirt, take out the PCV valve and throw away the screen - checking the small hose making sure it is not plugged up. If all looks good there, you will need to remove the intake manifold and replace the breather box.

Klaus
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Volvoless. Sold the R. There is now a void...