We hear time and time again how cyberspace yackers when dealing with tuning tell others to shitcan the MAF and use speed density as somehow hardcoding the airmass via the VE tables in the PCM will meet all engine and weather conditions.

Here again shows that is not so and that the MAF/PCM is much smarter in making the correct AFR changes.

Below is two testrun results that the top test was done 1 day and then another testrun done one day later.

All it takes is weather difference to change what the airMASS is.

If as example we took the results from day one as to what the reported airmass was ( via the OBD-II MAF parameters) and then compare it to the VE table in the PCM we see they do not match.
If we changed the VE table to the values reported from test 1 and then flashed that into the PCM we would see it was a waste of time as the 2 results below had zero tuning changes and only weather changes over 1 day and the resported values are different thus a moving target

Thus making changes we saw in test 1 would be valid over time and weather changes

Each results shows, at top values are what MAF reported, center is the percent difference from what MAF reported to what the values where in the VE PCM table and bottom values are what was in the VE table.

Notice how just one day difference in weather and how the percent difference changed.