Actually on an untuned car 980 AD counts is pegged - most tunes, including canned tunes will extend that to 1023 AD counts which is analogous to 5v.
To check the MAF, log RPM, MAF volts or MAF AD counts, one of the airflow PIDS, usually #/min, load (which uses MAF input to calculate it). If all those seem normal, as in MAF volts/AD counts, airflow and load all go up with RPM when driving, the MAF is probably OK.
Don