Increased throttle response is often confused with increased power (Since increasing throttle response reduces the time needed to reach higher RPM speeds and consequently provides immediate access to an internal combustion engine's power and makes a slow car equipped with that engine, for example, feel quicker[1]) but is more accurately described as time rate of change of power levels.
However, factors such as improper maintenance, fouled spark plugs or bad injectors can reduce throttle response.
Older diesel engines directly connect the accelerator pedal to the injection pump resulting in instant response.
[3][4] Throttle response in manual cars can be enhanced by dropping to a lower gear before accelerating.
The advent of concern about fuel economy and emissions had major impacts on engine design.