Codes 71, 72, 73, are probably related to the rough engine sound. This could be caused by too rich a mixture. Since the mixture is controlled by the computer it could be computer or sensor related. If the car is tested for emissions this would show up as unburned hydrocarbons, (raw gasoline). The A/F sensor problem would likely be the air/fuel sensor. In this case it is saying that the sensor circuit is malfunctioning. This could be the cause of the overly rich mixture that caused the 71,72, 73 codes, and the low gas mileage. So......fix the sensor circuit and five of the codes will go away, the car will run smoother, and the gas mileage will go up. Then deal with the other two codes. They might disappear as well if they are somehow related to the other codes.