MAF sensor specification

Not possible to say exactly as the unit reads airflow into the engine in real time and the flow rate depends on air density, temperature and altitude. These are the factory specs.

If it is adding fuel under load check the fuel pump flow rate. At idle the pump is providing adequate flow, at higher rpm it isn't keeping up so the system adds fuel to balance the mixture. Check the O2 sensors to see if they are dropping lower under load as that would show a lean condition as well. The sudden increase in flow at WOT is common, the number you want to see is what does it measure after the engine rpm stabilizes.