i had the left cat and abv valve replaced back in december. i still have poorgas mileage, about 21 mpg down from 26mpg. the tcs light is still coming on for about minute on a super cold morning and then it goes off after warm-up. the cel is not on at any time. any suggestions?

 

i have a 2000 2.3 w/116,000 miles. i called the mazda dealership, they are going to take a look at it on monday. they said that it may be the gas the stations in out cold climate provides and that i may see an increase in mpg. is that possible? anyway, any info would be helpful and appreciated.