Possible Causes and Troubleshooting Steps:
* Faulty Ignition Coil(s): Even though you *tested* the coil, a thorough test might be needed. A visual inspection for cracks or damage is a good first step. A more advanced test using an inductive clamp meter or a professional-grade scan tool would be better to verify each coil's output. One or more coils may be intermittently failing, explaining the random misfires.
* Worn or Damaged Cam Sensor/Crankshaft Sensor: These sensors tell the computer the engine's position and rotational speed, crucial for proper ignition timing. A faulty sensor can lead to misfires and MAF sensor problems because the engine isn't running correctly, impacting the air readings. Replace these sensors one at a time to isolate the issue.
* Vacuum Leaks: Vacuum leaks can disrupt the air/fuel mixture, causing misfires and affecting MAF readings. Carefully inspect all vacuum lines and hoses for cracks, leaks, or disconnections. Use a vacuum gauge to confirm if there are leaks.
* Fuel Injectors: While you checked fuel *pressure*, a faulty injector can still cause misfires. A clogged or leaking injector might not be easily detected by just a pressure test. A fuel injector test might be needed to check the flow rate of each injector.
* Wiring Harness Issues: Look for damaged, corroded, or frayed wiring, especially around the ignition system, MAF sensor, and engine sensors. A short or open circuit in the wiring harness can cause intermittent problems.
* Computer Problem (PCM): In rare cases, a faulty PCM can cause these codes. This is less likely if you've recently had many of the components replaced, but it's still a possibility. Diagnosing this is more complex, and usually requires professional help.
* Catalytic Converter: A clogged catalytic converter can cause backpressure, leading to misfires and affecting the oxygen sensors which may indirectly influence other readings.
Recommendations:
1. Re-check the ignition coils: This is the most likely culprit given the codes. Use a proper testing method to ensure they're all functioning correctly.
2. Check the camshaft and crankshaft position sensors: These are critical for proper engine operation.
3. Thoroughly inspect vacuum lines: Look for any cracks or leaks.
4. Test the fuel injectors: Ensure each injector is delivering the correct amount of fuel.
5. Check the wiring harnesses: Look for any signs of damage, corrosion, or fraying.
If you're not comfortable performing these tests yourself, take your Silverado to a qualified mechanic for diagnosis and repair. It's crucial to diagnose the underlying problem, not just keep replacing parts. A professional scan tool can provide much more data than simple code reading, helping pinpoint the issue faster and more accurately.
