89 bronco fault code

89 bronco full sized eddie bower edition. 351w, auto, obd fault code says o2 senser lean mix or low voltage. egr not closing. changed o2 senser twice, changed egr valve and pressure switch. code keeps coming up the same after i reset codes. even did a hard reset. any ideas? i'm wondering if i might have to flash the ecm.:banghead:

guess no one can help on this one?