Working on a 2012 VW CC. We diagnosed an issue with the check engine light "CEL" coming on and causing the vehicle to stumble and even stall a couple times. We replaced the spark plugs and then pressure washed and degreased the engine to inspect for oil leaks. We found that the crankcase vent valve had failed and was allowing the turbo to cause excess pressure on the crankcase making a couple of the oil seals leak. We replaced the crankcase vent valve and then monitored for oil leaks.