Your first post said it was a 70mm calibrated for 19's. Now I'm confused.
As a practical matter, the factory mafs can't be recalibrated. If you want to use it with 24's, you'll need a chip/pms/twEECer/tuner to change the injector size in the ecu. If it's a C&L, they can give you a different bolt in parts to calibrate for different size injectors. If it's a ProM, you must send it to them along with a small fee ($100 last time I had mine recalibrated) and they'll recalibrate it for you.
Oh - the Cobra 70mm factory mafs are calibrated for 19's, and the Cobra computer adjusts for the 24's -- so if you use a Cobra computer with an maf calibrated for 19's, you must run 24's.
Well look at it closely and see what make it is. I'm not aware of any ProM's that small. Most aftermarket maf's are at least 75mm. In any event, C&L - you recalibrate yourself by bolting in different electrics; ProM you have to send it off and pay them to do it.