Updated "P" Version, Genuine VW part

Volkswagen revised this part due to failing diaphragms inside the valve. Failed valves often cause driveability symptoms, including rough idle and reduced power due to boost losses. A failed valve may also cause engine oil leaks, and may result in vehicle emissions test failures.

The part itself acts as a PCV valve providing a one way exit for gasses built up in the crank case. When this ruptures it basically acts as a vacuum leak only less noticeable.

Note:  Latest revision from Volkswagen, factory part.