l have a '91 Sabaru Legacy, automatic transmission, not turbo.
I've gone through the 3rd mass air flow sensor in about a month.At first l thought (they're rebuilt) maybe they were defective, but now I am beginning to suspect that something is making them fail.Maybe an improper voltage to the unit (and what causes that)?Dirt getting into the air-passage (it has a new air cleaner)?

Thank goodness the auto parts dealer is standing behind their warranty, they're $200 + bucks a pop!

Help!!Thanks, and l appreciate any advice.

If they are truly rebuilt units, then l would suspect that you are getting faulty units.

It is not too common that you would find reman electrical components. If in fact you are getting reman parts, they is a good chance that they are defective. Other than that, causes of the failures may be related to water getting past the air filter, a dirty or over-oiled filter element, or corroded connections.

MAF sensors are very delicate in the sense that they need to be clean, and free of carbon, dirt, oil, water, and so on.

91 Legacy is had computer problems. You may have the computer shorting out the sensor.