More tinkering with the ECU settings.
I decided to let the narrowband re-map the power map dynamically.
I can always instantly switch back to the base map if required - in the meantime the experiment is to see if the ECU can work out for itself the correct fuelling to hit the 14.7 AFR.
This will obviously optimise for mixture rather than power
Test run today of about 60 miles showing the adjustments, percentages +- which are recorded, remembered and applied over the base injection map automatically by the ECU. Mostly country roads some village drive at 30, some coasting behind traffic, some more spirited 60 mph - so a reasonable sample (sans motorway driving)
Looks like I was rich at idle and lean in that middling acceleration area.
The following graphs showing before (top) and after (bottom)
Left-Right is RPM, Bottom-Top is fueling, Front-Back throttle position.
The graph shape showing some reduction in fuelling at idle speed, but also small changes across the board, but nothing upsetting the overall injection map shape.
I'll leave it on this mode some more and take another look after a longer period.