IS this the aim of the 'best fuel map?' to Keep the
AFR at the optimum figure at all times?
or is there conditions where a richer or leaner AFR would be
more ideal?
Optimum for what?
Optimum fuel economy is leaner than optimum power.
Depends on what you are mapping for.
Typcially it will be a bit of both, at different points in the rev range, well on a road car anyway.