I think what he is saying is that the engine is being held back electronically to make sure it leaves a gap between Maserati and Ferrari. A few years back it was reported that the 3200 was electronically detuned to make sure it didn't produce more power than the 360.
The suggestion is, if you can remove this detuning software, the engine can perform to the best of its ability.
That's what I mean.
About the previous post: 14.7 is the stoichiometric air/fuel ratio. It is not true that this is the "ideal" ratio. Sure, it is ideal for emissions, since the 3-way cats cannot cope with a ratio that strays too far from 14.7 (hence the O2 sensor that provide a feedback loop to keep the engine from running too rich, and as a consequence limit the amount of power). Full load operation is outside the "emissions control zone" in most countries (I believe also in the USA), as both the ECE and US light duty transient cycles used for emissions calibration are at very light load. So there is scope to go a bit richer where the emissions are not regulated, and gain a little more power as the excess fuel also helps to cool down the cylinder heads.
I believe that even without disabling the feedback loop of the O2 sensors (which would require complex SW reprogramming) it would be possible to increase the fuelling curve of the 4.7 to reach full-load figures close to 500 HP. Add a set of low resistance air filters, a fuel cooling system and low restriction catalysts, and I am sure that we would go beyond 500 HP without having touched the engine mechanically.
There are limits, of course: it could be that the camshafts have profiles that do not allow an aggressive gas exchange at high rpm, thus limiting the amount of air that you can get into the cylinders - and hence limiting the max theoretical power (fuel needs air to burn...). It wouldn't be too difficult to redesign the cams but it would require a lot of experimental work and an instrumented engine to assess what the temperature/pressure limits are.
In conclusion, I think that without opening the engine you could probably achieve 500 HP within the safe temperature/pressure limits that the engine can take without compromising reliability. And because the engine is so big, you won't need to increase the red line either - 7500 rpm on a 4.7 litre is plenty enough to pump a lot of air into the cylinders!
As a second stage, one may contemplate playing with more aggressive cam profiles and maybe push the rev limit a few hundred rpm higher - although this would cost more and would inevitably result in a peakier engine, with less torque at low rpm.