So, my 97 fire has been getting really bad gas milage for a while now. I changed my front O2 sensor about 2weeks ago as some members on here suggested to do. Everything was fine. About 10 days after the CEL came one. I used my OBDII reader to check it and it pulled 2 codes:

P0171: System too lean (Bank 1)
P1441: EVAP canister continous open purge flow, or high-voltage during non-purge

I cleared the codes thinking maybe these CELs were thrown because the PCM was comparing new values to old values (which might have been faulty due to a potentially bad sensor). I haven't driven the car since I cleared the codes, and I do hope that was the problem - but I suspect they will come back once I drive the car again. Any thoughts, suggestions, advice etc.?

Thx