All modern vehicles use an ECU (Engine Controll Unit) to control fueling. When the manufacturers write the program for fueling at full throttle they tend to program for best economy rather than for maximum power. We set the fuel ratio for best power at full throttle this allows us to modify the program at mid range throttle so that over all fuel consumption is improved.
Fuel ratio for best power 12.6:1
Fuel ratio for best economy 15.4:1
Ignition (spark) timing is also controlled by the ECU this is also an area of adjustment that will release power from an engine. Years ago it was possible to adjust the distributor to adjust timing and replacing the internal centrifugal bob weight springs to help with advance curve, modern day engines no longer have distributors so the only way to optimize ignition advance is to remap the ECU to give a more advanced timing curve resulting in greater power and more responsive throttle.
Forced Induction (turbo/compressor)
Forced Induction is the process of using a mechanical system to force more air into an engine. This includes superchargers, turbochargers and other mechanical systems. Both superchargers and turbos use a compressor to force air into the engine, making it more dense (i.e. more oxygen). When fuel is added this creates a much larger explosion and more power from the engine. These mechanical compressors are controlled by the ECU, remapping the intake boost pressure gains as much as 40% more power.
Fuel map Ignition map
Forced induction map