I have an 03 Forester. It has about 115k on the original motor.The check engine light came on a while back. I took it to my mechanic and he diagnosed it to be the mass air sensor. Since the car ran fine and I did not want to spend $400 plus on a new one I contunued to drive the car. Since the weather has gotten very cold up here in New England and the heat has been on I have noticed a strong gas smell when the heat is on. I checked under the hood to look for any leaks and cant find any. Could the mass air sensor be the cause of the smell? Any suggestions?