Misfire 4.2 BFM

[mcs]

Hello.

I was using my A8 to explore the length of Australia's east coast last week and I experienced what felt like extreme misfiring. The symptoms were:

Car made popping noises
Extreme loss of power
Had to rev the nuts off it to maintain speed.

These are most acute at highway speeds on light throttle when climbing a gradient.

It seemed that it was bad fuel at first because its never done it before and the car was driven many highway miles the previous day without issue. I parked the car and went to the beach, left it an hour or so and it drove fine.
The next day it was fine again until about the 3rd hour of highway.

It was 37 degrees C that day also.

The car actually misfired so badly the engine stopped twice.

The codes I got when I arrived home were:

17538 - fuel trim bank 2 (multi)
P1130 system too lean

17536 - fuel trim bank 1 (multi)
P1128 system too lean

No codes for coil packs or plugs and all have been tested and renewed in the last service.

Fuel pumps are ruled out as the car is fine after a restart (yes, I am aware that the secondary pump is activated after 3000 revs or a restart idle) but the car drives fine only until a few hours of highway.

I cleaned the MAF yesterday and I will take the car out on the highway again soon to test it.

Any other ideas?