If the upstream O2s are originals, change them out. Don't use cheap ones. Clean the maf sensor. Change the PCV valve (inside intake under removable cap on top). Reset the fuel trims afterward with a scan tool. After that, use a scan tool, watch fuel trims at idle and cruise. If you are using regular pump fuel with ethanol, mileage suffers. E10 or E15, expect losses in fuel mileage up to 3-5 MPG over ethanol free fuel.
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