400 hp Alfa Romeo 155 Q4'

[kunev]

A particular chip have to be written for particular injectors capacity and base fuel regulator pressure, otherwise fuel delivery will not be correct.

[Steve Webb]

A particular chip have to be written for particular injectors capacity and base fuel regulator pressure, otherwise fuel delivery will not be correct.

Thats true, however to think that your injectors are delivering fuel in exactly the same way they were when they were new, or that your fuel pressure regulator is behaving the same way now as when it was new is plain crazy.
Sure to get the maximum power out or a partiucular setup, the chip will need to be written for the car at that period of time. But with a wideband AFM, changes can be made to the setup keeping things safe, until the chip can be rewritten.
And as we all know, changing the injectors on a Q4 is not the easiest of jobs, and no something that you want to do whilst waiting in line for a rolling road run.