They do work. Done by remapping the ignition curve to suit a higher grade of fuel. Original Kia spec is from 87 RON gasoline. Powerchip is 91, 95, or 98 RON

All they do is remap the chip (in old terms, advancing the ignition curve a few degrees) and derive a new CRC checksum and save that to the correct location (computer geek talk - ensures ECU self check is OK).

The most significant thing is you need to use the correct grade of gasoline or higher than the chip you put in to get the effect. Using a lower grade of fuel will not hurt the engine, but it will misbehave a bit until it learns that it is dealing with a "bad batch". It will also take a tank or two to get back to normal once you have the right fuel in it.

There are no single "in-line" adapters (from airflow meter or the like) that will work in any petrol engine. Don't be tempted by the cheap "adapters" off Scambay, all they are is a 2 cent resistor that richens up the mixture (eventually stuffs your O2 sensors and won't pass your smog checks).