Its not really a question of calibration both original and these are 19lb@ 40 psi.
If the old injectors were very dirty and delivering an uneven amount of fuel or poor flow across the board the ECM will try to compensate.
It does a good job of masking things and keeps it running well enough unless one is so plugged it causes a misfire.
The new injectors have better spray pattern and better atomization, with all 6 flowing the same rate the O2 will not be signaling for more or less fuel at the rate the old ones were so fuel trims will remain stable with very little drift.
I would also expect throttle position to be be less to achieve the same performance. All these things can certainly improve fuel economy.
So basically when you hit the throttle the inputs are from the TPS, MAF/MAP, RPM, crank/cam sensors, front O2, rear O2 to monitor the cat, VSS, temp, etc.
Outputs are going to the throttle body (if equipped with an electronic unit), IAC, injectors, PCV, transmission control, fans, VVT, timing, and so on depending on how the car is equipped.
The ECM cannot speed up the injectors, that depends on rpm but it can adjust the pulse width in milliseconds (on time) to increase or decrease flow this happens anyway depending on load but clogged injectors can trigger this.
If one or two injectors (or more, just hypothetical) are iffy the ECM will increase fuel on all of them on the bank monitored by the O2. In this case a 6 cyl with one O2 and two iffy injectors will have 4 injectors flowing more fuel to keep the O2 happy at 14.7:1, because the two iffy ones are running lean.
So the end game is four cyl can be washed down with fuel causing excess fuel dilution in the oil and two are running lean but as far as the O2 and ECM is concerned everything is fine until it has to add so much fuel it trips a CEL.
The engine will require more throttle to achieve the same amount of power because of the two cylinders are not contributing their equal share.
Sorry for the rant, i probably left a lot of stuff out and didn't include all the sensors but this is just an example not an actual make and model and i'm sure i will hear about it but you get the idea.
