As you can see (pictured below) these breathers do not lead a very clean life and require replacement periodically. Also these breathers are often modified and improved versions of the original factory fitted design.
When does my block breather require changing?
As a service measure (we would advise replacement at 40,000 miles). Change with swirl flap modification. Change with replacement of turbo charger.
You can see just how much the breather filter expands over time with oil saturation and is beyond it’s functioning life. This is a relatively inexpensive service measure, when was yours last changed?