2009 Chevrolet Silverado 5.3L Troubleshooting: AFM Delete, P3104, P3425, P0455, and P0442 Codes After Custom Tune

Model: AFM Fault Code: P0455 Posted: 2021-06-24 06:30

Hello everyone, I'm Jessie. I recently purchased a 2009 Chevrolet Silverado with a 5.3L V8 engine. After performing an AFM (Air Flow Meter) delete as recommended by my tuner, I've started receiving several diagnostic trouble codes: P3104, P3425, P0455, and P0442. Additionally, I'm seeing a random misfire code (P0300). I followed the advice of Diablosport to perform a custom tune after removing the AFM, which cost $140. While the vehicle runs smoothly under acceleration—clearing up all codes when I press the accelerator—the idle is rough and unstable. The issue persists even after the tune, and I'm concerned about long-term engine performance or emissions compliance. Could anyone provide insight into what these specific codes mean in this model year and whether an AFM delete is safe or necessary? Any guidance on resolving P3104 (AFM circuit malfunction), P3425 (fuel pump control circuit issue), P0455 (evaporative emission system leak), and P0442 (EVAP system small leak) would be greatly appreciated. Thanks in advance, Jessie.