for those having issue with fuel average, please connect scanner and check your fuel trims, LTFT and STFT the ideal value for STFT is +-5 and LTFT is +-10 anything beyond this mean ECU is compensating too much for fuel that means either you have blocked cat, faulty o2 sensor or worse case high milage engine which has lost its compression assuming you have clean MAF sensor and Air filter..
PRO TIP.. check you O2 sensor reading at idle if it is oscillating between 0.00 to 0.09 or max 1.. static or less oscillation mean CAT or 02 faulty