Button, you are right that a modern EFI always can balance air and fuel. But if the air is very hot it will dose less fuel to keep the balance of the mixture so the result means less power. If the air is colder the EFI will also keep the same balance but it will deliver more fuel to do so and you have more power. As far as I know, this applies at least to the partial load range. For full throttle one should adjust the ECU to the air volume and temperature. I am only an interested layman and other TM members can explain this topic much better but in one point I am very sure, your your brain works totally very well and it is in best order:)
