Test when cold.
Test when hot.

Readings change from OK to bad, then your answer is yes.
Used AFM from a junkyard is not that much.

AFM tells fuel pump to run (or not). Fuel pressure regulator and engine vacuum tell what pressure the fuel is at. ECU tells injectors how much fuel to inject based upon AFM, TPS and O2 sensors among other things. http://www.autoshop101.com/ tech articles are a good read.