MAF range of slot style meters is 100% tied to the size of the MAF housing you place it in and whether or not you are setup in a draw through or blow through configuration. You could probably support 2000hp in a 10" MAF housing, but meter resolution in the low rpm's would be non-existent due to poor velocity and I am sure terrible turbulence.
Having said that, what intake and MAF housing is being used? Only then can we tell you what the capacity is.