Just had the same problem - but not high fuel consumption.
Changed all sensors (battery disconnected)!!!

wait overnight

Start up in P - do not touch steering wheel no AC - idles for 3 minutes ....you can notice how the ECU "plays" and adjsust.
Same in N

Same in D
and again with a/c on

do not touch the steering wheel!
Run engine in D again for a few minutes - see if it is stable.
OK?
Stop engine and switch to instrument position right away and hold down the accelerator pedal for over 1 minute. This fixes the position for the ECU for the gear box. It is all in the GREGORY!!

All done?
No good ? Sh.....
Happened to me - second hand ECU installed -- all the above again --and running like a clock..
I wondered why nobody ever mentions the ECU ...too
(yes ---you did MUzza

Fairgolf