In the early days of performance optimisation, the computer chips on which all the relevant information was stored were removed using a soldering iron and replaced by new memory units with optimised data. The term "chip tuning" is derived from this technique.
These days, this method is only still used on older vehicles. Most control units are fitted in such a way that they can be read and reprogrammed by means of onboard diagnosis: the engine control unit is connected to a computer via a plug-in connector in the vehicle's interior. This enables the performance to be optimised cleanly without leaving any visible traces whatsoever.
An alternative method is so-called "flashing", which involves removing and then reprogramming the control unit.
