2003 Kia Sedona P0141 Code: Front Bank O2 Sensor Failure After Exhaust Replacement

I'm having serious trouble passing my annual emissions test, and I've already failed it twice. Despite spending over $450 on repairs, the vehicle still fails. Here's what I've done so far: - Replaced both front O2 sensors (before and after the catalytic converter) with OEM Bosch parts. - Replaced the front exhaust pipe where the two O2 sensors are located, directly after the converter. - Replaced the rear O2 sensor located after the catalytic converter on the back of the engine. This is a 2003 Kia Sedona EX with a 6-cylinder 3.5L engine and dual catalytic converters—one at the front and one at the rear—currently showing around 112,000 miles. After my second failed emissions test, the diagnostic trouble code reported was P0141. The code specifically points to a problem with the oxygen sensor on the front bank (front of the engine), though I'm concerned it might not be related to the O2 sensor itself. I understand that P014 or P0141 typically does not indicate a faulty catalytic converter, but when I replaced the front exhaust pipe, I discovered that the front catalytic converter was completely empty—no honeycomb structure remained inside. This raises my concern: could a damaged or collapsed catalytic converter be triggering the P0141 code? I’ve avoided replacing the converter due to its high cost (over $250 for just the part) and the difficulty of accessing it during installation. Could a failing front catalytic converter be causing the P0141 fault? Any insights, suggestions, or technical explanations would be greatly appreciated. Thanks in advance for your help.