I'm no mechanical engineer, but I can't see how the ECU could compensate. The problem is a reduction in the amount of available oxygen and nothing the ECU could do can substantially increase that in a normally aspirated engine.
It could certainly make the fuel mixture less rich to match the reduction of oxygen - so no fuel goes unburnt. I think that would save gas, but would not increase power.
My understanding is that forced induction via a turbo or a supercharger is the only way to compensate for reduced air/oxygen pressure.