We are talking about MAFs not injectors in all my dyno tunes if you are running 42lb injectors and a matching 42lb MAF the injectors will max out before the MAF. I have had some blow-threws that would peg meters but that is to be expected.
The problem is the majority of people dont know how or that they need to change there displacment to keep the load tables in check. If you just slap on a MAF calibrated for 60 lb injectors then your fuel and timing maps are all out of wack. Sad part is many tuners i have spoke with really have no clue what they are doing either. Pro-Ms are hard enough to tune, i have had the best luck with OEM ford MAFs like the lightning 90mm. Hell im running a 89MM Pro-M calibrated for 24lb Cobra and its good for over 350rwhp, BTW point 29 on my meter is 4.55V 1406.75 KG/HR above the 89-93 SCs MAX 1,400kg/hr so why go any bigger then that???