"Diesel. Remember what this street smelled like in the old days?"

In this quote, Amir asks Farid if he remembers the smells of the street years before. This is significant because it alludes to Amir's childhood in Afghanistan even though in America, Amir himself has mentioned that he preferred to forget the past and leave his sins in Afghanistan. However, since he is back in Afghanistan, it is hard to forget the past since the places he knew when he was young are, although falling apart, still where they were years ago.