You can test for the poppets being stuck, but you need a scantool and a fuel pressure guage, Scantool will power pump to the set pressure(55-65psi) and will open 1 injector at a time, if the pressure doesnt drop when one injector is powered up then poppet is stuck. If poppet is stuck then I strongly reccommend the update injector assy(complete unit) from napa or Gm. When one poppet failes the others arent far behind, the new style is a complete redesign and is much more long lived.
This is the diagram for the injectors. Airflow meter is located at airfilter connection to throttle tube. The PCM grounds each injector , the pins should be labled in tiny stampings on connector or harness (c105)