During cruise conditions, when at correct operating temperature (no additional cold engine fuel), yes, 14.7:1 is the AFR that gives the most complete burn of fuel and cleanest emissions.
I tried a 3SGTE AFM on my supercharged AW11 years ago and it wouldn't work without significant signal modification. In fact, I never kept it, I just returned to my Mazda AFM housing (same size the 3SGTE), with the original GZE circuit board in it and continued using my Jaycar Digital Fuel Adjuster. It was actually easier to use the DFA and the Trust Emanage Ultimate (which can modify load sensor signals but I only used it to intercept the injector signals) than get the EMU to correct the AFM's signal, but I only road tune
Remember that the fuel side of things is only half of what the load sensor does. It also has a huge influence on the ignition timing.
So if you put a bigger AFM on an engine, it will show a lower load signal to the ECU for a given air flow. Now you might be able to get slightly bigger injectors that flow near enough, to get the right fuel flow for the given lower injector open time, to allow the engine to run decently.
BUT(!!!) because the ECU will always be seeing a lower load than what is really happening, the ECU will deliver MORE advanced ignition timing. And that extra advance may be enough to cause severe knock!
This is why I suggest keeping sensors and ECU's together. Unless you are running out of sensor resolution (which will happen and does happen surprisingly early in the early AFM equipped GZE systems) and have a means of tuning the signal before it goes to the ECU (and even then, I'd only recommend an interceptor tuner like an Emanage Ultimate), you'll be opening up a can of worms.
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