What are the symptoms of a MAF gone bad? This for future reference. My Q runs as new.

rough idle

Perhaps the best way to experiance it, is to disconnect it and try to drive.

I had the oil changed with the last tire rotation and they left the MAF unplugged. It took about 10 sec. to figure that one out! But it did scare the HELL out of me as I almost got run over trying to turn left.

Once you feel the car with the MAF Disconnected, it won't be hard to diagnose when you start having problems.

Make sure you clean the connectors when you remove it, they are often very dirty and cleaning them can make a difference.

The MAF test manual pages EF & EC 114-116 show how it's wired and you can probe the connector and read the return voltage to ECU.1.1-4.4 volts depending on air flow [very very non linear] as the 4.4 would only occur at 6,000 rpm WOT mostly around 1.2 -1.4 volts even at 60 mph cruise.The MAF has a range of roughly 10-255 grams per second.

Without a MAF signal voltage [or a very incorrect one] the ecu guesses by TPS and rpm and will not rev above 2,000 rpm.

We see very very few failures of the unit itself just connector corrosion or those that get dented on top where the electronics are located [under the black square].

Same with the CAS until very high mileage when rust [bearing] may cause errors in the 1 degree wheel [spark scatter or signal drop out].