Ive had quite a few VW where the coolant temp sensor goes faulty and says -40 degrees c so its very rich on start up and will choke the plugs up if not driven off straight away. Also it dosent always throw up a fault code as its not open circuit.
Have the vehicle from cold and check the live data from the temp sensor during warm up with your scanner.
Also try wobling the wires on temp sensor as they are sometimes loose inside the sensor.