i just bought this 1999 a4 1.8 turbo and it has 207k miles on it. im not that familiar with this brand of cars but every time im uphill or downhill the car shoots a cloud of smoke. i was guessing it was the head gasket. its marking the O2 senor could that be the reson? its only white smoke tho and it only does it uphill and dowhill and big clouds of smoke. dose anyone know what could be the problem?