This company offers water injection systems and programmable fuel injection controllers which are supposed to replace or supplant the built-in chip. The concept of water injection is that the air charge to the combustion chamber might be too hot and lead to preignition/detonation/knock. This is unlikely ever to be true in any normally functioning engine designed to meet OBDII emission standards - among other factors your car's EGR system controls inlet air temperature to smooth out combustion (that is its purpose). So does the intrinsic design of the air inlet system.

Regarding user programming of the fuel system, it is also unlikely that any car manufacturer's fuel system would be by design so poorly programmed that a simple amateur device could do nearly as good a job as the original, no less improve on it. Again, you can't market a car which does not meet emission standards, which already require designed-in fuel system programming which is quite close to optimal.

Can you imagine that injecting water into a car engine would not damage good lubrication and long-term durability?

Before buying into anything like this I would want to see its benefit demonstrated in extensive controlled tests by an independent agency.

If the car now doesn't perform properly, I would look into finding and repairing the specific problem(s).