Mass air meters are not "calibrated" to injectors. That's only sort of true if you have an aftermarket "calibrated MAF for X# injectors". Don't confuse the two.
If you get a 90mm Lightning MAF and 42# Lightning injectors and stick them in your car, you'll find out real quick that it runs very badly. Aftermarket MAF guys skew the MAF readings so that the MAF puts out less voltage at the same airflow than a stock MAF does. This way, the computer sees the lower voltage, and commands a lower pulsewidth (to a larger than known injector). While that stinks, at least it somewhat works. Proper MAF and injector calibration would be much better.
Any time you change the mass air meter, inlet tubing/air filter, injector size, displacement, or radically change the amount of airflow/horsepower, add boost, a decent sized cam, or fuel pressure, you need a tune to compensate.
If you bought a Quarterhorse and tuning software, you're about to find out just how complicated tuning can be. If you don't have a good handle on how to do it, be prepared to learn a LOT, or consider having another tune written by a competent pro tuner.
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