The stage 2 fix is expensive for what you get. However the fsi engine recirculates alot of oil and petrol vapours from the engine and much of the oil vapour condenses in the IC. Not really something you want happening.
The oil vapours that make it through the IC have a tendency to coat the intake valves making air flow turbelent into the cylinders as the deposits build up.

The catch can minimises both the IC condensation and oily deposits on the intake valves thus making it a good preventive fix if you want to keep your car running at its peak.