HI I have a 2014 I4 turbo with lil over 92K miles on it. For the longest time I have had a P0420 code on it . I replaced the front O2 sensor and code cleared for a a couple of days and then it came on again. I had a smoke test done to get the true diagnostic issue and said needed to replace the catalytic converter. I had that done over the weekend and after driving the vehicle to work this am (bout 30 miles or so ) it threw the code again as well as a code P0171 at the same time ( had car read at lunch ). Can someone please tell me why i am getting this code again and the significance of it and the P0171 together. Thank you .