New Cat and O2 sensors?

97.5 GS...Car has 122,000 miles on it....A while ago after it was tuned up MPG's has not gotten better. It gets about 10-11 city and 22-23 HWY. It still has original CAT and O2 sensors... IM not getting any SES codes. Is there a chance if i replace the CAT and O2 sensors my milage will get better? I also heard there are 2 O2 sensors. I know 1 is located at the u-bend. Where is the other 1?

97.5 GS...Car has 122,000 miles on it....A while ago after it was tuned up MPG's has not gotten better. It gets about 10-11 city and 22-23 HWY. It still has original CAT and O2 sensors... IM not getting any SES codes. Is there a chance if i replace the CAT and O2 sensors my milage will get better? I also heard there are 2 O2 sensors. I know 1 is located at the u-bend. Where is the other 1?

Look behind the rear bank cylinders towards the firewall at the exhaust downpipe for 02 sensor position 1.

Thats pretty low mileage. I'd start with the 02 sensor before the CAT first, then monitor and decide whether to replace the CAT and rear 02 sensor.

The 02 sensor can get to 60% efficiency before triggering a SES light or 02 sensor DTC error code.