2005 Golf 5 2.0 FSI, Tiptronic Japan. The car sometimes produces some sounds/knocks when changing from gears 1-3 as if there is some kind of stress on the gearbox hence there is no smooth changing over more especially at these gears. The engine warning light has been on ever since the problem started. This has affected the performance of the car. The car also vibrates or shakes at the front when travelling between 60-90km/h.I have changed the fuel filter, fuel pump, serviced the vehicle, changed transmission oil twice within 6 months and have also replaced the front bearings and even resetted the car twice after servicing and changing of transmission oil, but the engine warning light still persist. What could be the problem, how can I rectify it and how much can it approximately cost me?