MAF (Mass Air Flow) Sensor testing?

[rocksteadyX5]

Is there a definitive way to test the MAF sensor to determine if its going/bad?

Problem (2002 3.0i): CEL is on and it failed emission testing. In the pass months I changed the Pre-O2 sensor, replaced the crack intake eblow, Replace the DISA valve (It was about to break off), Changed the Spark plugs and coils. Still I can't get the CEL to clear. The only thing that has not been changed is the MAF.

I scan for codes and see misfire in 1 & 2 and code for Pre-o2 sensor.

I plan to switch around the plug on 1 & 3 to see if it follows. Wanted to test the MAF before changing it.

Any thoughts or idea would be great.

Thanks