2000 Ford Ranger P0155 O2 Sensor Fault: Diagnosis and Fix After Replacing Front Sensors

My 2000 Ford Ranger is displaying fault code P0155, which indicates a problem with the oxygen sensor on the driver's side. I have already replaced both front O2 sensors, but the P0155 code persists. There is no visible wire damage or obvious signs of exhaust restriction. Recently, my truck has started hesitating when accelerating—specifically, it doesn't respond to gas pedal input as expected. It feels like I'm not pressing the accelerator at all, even though I am. What other diagnostic steps can I take to resolve this P0155 issue? This is currently the only code appearing in my vehicle's system.