what our groove (and other techniques discussed here) SHOULD do is to reduce overall consumption and narrow the range of variation.
fuel trims at zero - all that means is that you (well, the vehicles computers, actually) have successfully re-written the fuel delivery map and the engine/powertrain is optimal.
do you keep track of your mileage/fuel consumption? If not, you should - my instantaneous and average fuel consumption readouts in the car do not match what my fuel tracker app tell me.
consider that the ratio of fuel vapour to air that gets burned changes based on the density of each on any particular day - that means that temperature and pressure have an effect on fuel consumption...MASS air flow sensor, manifold ABSOLUTE pressure sensor, intake air temp sensor...there is no way you'll make a non-stationary engine in an uncontrolled physical environment have rock steady, predictable fuel burn...especially when you add your right foot to the equation.
you don't need to replace your computer; for what it is, the machine is operating as optimally as it can. (Good work!)
EDIT: what does the MAF report in terms of grams/second at idle in closed loop? My understanding is that it should be near the litres of displacement of the engine, in this case 5.7. If it’s above 6, you’ll want to pull that back. MAP modification may be in your future, Michael. Less air = less fuel, remember.