Getting more technical,
With different Gaz Octane and air mixture you need to reach a different compression - mixture of air and gaz, temperature where you time the spark plug to ignite the mixture, providing a better more powerful explosion.
The Diablo sport have already tested settign and can modify your computer in the car by flashing the software with more accurate timings for Octane and air system on the car you use. In older days where flashing was not possible people swap the computer chip with a different software inside.
An other thing you can do with the Diablo sport is change when the transmission computer shift gear. for example the current setting on the car are made for daily driving with in mind fuel economy, and sometimes abuse a little the gaz. The computer determine when the gear shift happens, So if it's in a save gaz mode, it might shift at 2500 rpm, but when you give it more gaz it will shift higher near the max HP windows to give good acceleration. By changing the setting, your daily drive might be, 3500 rpm is when the car shift gear, meaning you always get that power feeling.
It's a lot more complicated then that, I do not recommend to do this alone. Diablo sport can build custom Firmware to be flash in the car if you have special equipment, but they have Base firmware to flash your car to what most people use, like go from 87 to 91 or 93 octane gaz. CAI installed or not etc etc, you can also modify wheel size diameter to re calibrate speed gauge and many more things.
Even if my explanation is more accurate this time, it is a general explanation.