Walter, here is the thing about spraying MAFs.
Ones in 3.9L engine are "heat stripe". Ones in 4L engine (or at least D2s, that i seen on pictures) are string in middle of things. Principle on how it works is dead simple - its thermoresistor. It is still beyound me why they cost so much. But then TPS which is potentiometer and those temp sensors (thermoresistors as well) are around 100$ too. Go figure.
So actual reason behind whole thing to not spray it are:
- protective layer will be damaged
- you will leave some liquid and then it will boil (thanks to exhaust nearby) and create conditions to damage thermo stripe/string. Also if its going inside those tiny holes too dip it may shorten wires.
Thats about it. If you aware that you got to clean thingy throughly, and if you let it dry and you know that cleaner didnt contain any oily substances (as they wont evaporate) and wont leave any residue - its ok to spray/wipe.
I cleaned mine when i got truck, and cleaned it recently. And no light came up. Its just that most of people, unless warned throughly, will drown poor thing

And i dont have 12 yrs of exp. in delicate electrical systems.