Heard a pop then Loud whining noise when let off gas pedal
Neutral and rev engine, no change, usually not audible on acceleration, has gone away a couple times only to start making noise again a short time later

I have changed Idle control valve, mass air flow sensor. I am puzzled as to what the issue still is. The car starts and idles fine but when I press the gas pedal it dies. Does anyone know what the issue could be