I think you mean MAF as in the Mass Air Flow meter. Yes, you can get a MAF calibrated to different injectors. The stock maf was calibrated for 19lb and the cobra's had 24lb.
You were correct with MAS. However, it's more commonly known these days as the MAF meter. As a matter of fact, I think it's always been a MAF meter on 5.0 mustangs. GM used to call them Mass Air Sensors. Maybe they still do, I don't know . Both of them fuction the same...incoming air passes over a hot wire. Guess it just depends on what circles you run in as to the terminology.
In answer to your question: some meters require electronic recalibration (i.e. Pro-M) and some can be setup for other sizes of injectors by changing the sample tube (i.e. C&L)