How do you test a maf?

If you have a handheld tuner you should be able to view the voltage signal that is produced from it. I forget the exact voltage values, but going from memory of the last time I viewed any such data it will produce about 0.8 volts at idle, and will steadily increase as throttle is applied, and a quick snap of the throttle should send it briefly up to almost 3 volts. It should increase/decrease steadily, with no sudden spikes, and at idle it shouldn't fluctuate very much. The MAF is a rare sensor to go bad unless there is physical damage to the housing or sensor.

Wow, it's been a while...

That's strange that your scanner gives a lb/min value for MAF reading [scratches head]. About all I know about that sensor is that the air flowing through it causes it to generate a low voltage signal which the pcm then uses to calculate airflow into the engine, which is why the only MAF values I'm aware of are voltage. Never heard of the one you mentioned, but I bet with a little digging around there's probably a way, some mathematical calculation, to convert that reading into a voltage reading.