Camshaft Cover Breather
WARNING: This page is about a different car, the 2018 Jaguar XE. However, it is still accessible from the selected car via links, so may be relevant.
Piston blow-by gases that enter the camshaft cover are drawn through the baffle valve and into the clean air Low Pressure (LP) intake duct by a venturi effect of the clean air passing the hose connection. Oil vapor is collected in the baffle valve and drains back to the cylinder head and the oil pan.