Every since I had my fuel pump replaced on my 92 Volvo 940 my fuel mileage has gone from 15 to 8 miles a gallon I just took my car to the inspection station and my CO reading was 4.23 percent limit is 1.20 so there's definitely something going on with my car any suggestions? I'm at my waits end with this gas mileage and now I have to get this car to pass Inspection thank you in advance