Engine turns over but will not start unless u hold the gas, on 1995 Mazda Protege

changed filter screen on fuel pump,new fuel filter,new distributor cap and rotor,new wires and plugs,at my wits end also voltage regulator replaced,please help

Asked by for the 1995 Mazda Protege
Clean the mass airflow sensor.
Thank U so much,is this the only thing that could cause it to act like this.