2008 Chevrolet Suburban 5.3L Stock P1174 Code Persists After O2 Sensor and Spark Plug Replacement

I've replaced both spark plugs and the O2 sensors, as well as the fuel cap. The P1174 code appears after a day or four of driving and then reappears consistently. I've run injector cleaner through the system multiple times, but the issue remains. With 127,000 miles on the vehicle, I'm considering replacing all injectors—could they be failing at this mileage? The P1174 code specifically indicates a cylinder-to-cylinder air/fuel ratio imbalance in Bank 1 only. I want to ensure that my vehicle remains stock with no aftermarket modifications such as performance air filters, cold air intakes, or non-OEM components that could affect emissions and fuel delivery.