Interesting calculation! As I expected Dewpoint has a big influence... This is the only real problem of a MAF: it measures mass. Air mass but also humidity mass.

So with umid air the MAF will "see" more air than what it really is, causing more fuel to be injected. At this point the O2's will notice the difference and cause negative fuel trims.
Right?

In my company we have a couple of gas flometers: they are similar to a MAF in their function.
There's no chances to have a correct reading if we don't have a drier installed before them!

So what to do? Install a big drier in front of the car?