Not an expert at reading that but it looked consistently like the A and B banks were different and also both rather high. Again, all disclaimers apply. This might help though to diagnose if the sensors are at fault or if they are reporting a fault..
Did you change the Air Flow Meter at the same time as Air Filter in December? These affect performance dramatically and if a cheap aftermarket jobby might just be culprit.
A bit obvious, but not a leak anywhere is it? Petrol with evaporate without leaving a puddle anywhere, and in this chilly weather will not be obviously smelly unless garaged. Tyre pressures & binding brakes already mentioned, you`ve not fitted a huge roof rack & top-box, have you!
no roof rack, tyre pressures all OK, dont think theres a leak. The mpg display would not be affected by a leak would it - thought it was a measure of fuel injected into engine??
That *.txt file shows no reading from Bank A HO2 sensor. It could just be the hardware you used.
Not being one to state the bleedin' obvious, but wouldn't it be worth the cost of a 10 minute T4 session (probably £25 worth) to find out what the stored DTC's are?