I have a 2.0 2000 Beetle. We have recently replaced the water pump, timing belt, o2 sensor, plugs and air filter. However, when it is cold outside it will not start. Then if it does start it stalls out. Later in the day is fine once it warms up outside. Once the car is running it drives great, however it is getting terrible gas mileage. It went through almost 3/4 of a tank of gas in less than 50 miles!! It is now giving a code for the mass air sensor however our mechanic is not confident that this will fix the issue. We have dumped over $1500 into it in the last 2 months, any help????