First post2012 1500 5.3 failed inspection for emissions. Check engine light actually came on as mechanic pulled it in the bay. Nuts! Just had oil sensor replaced and codes cleared a few days before.Air/gas mix was off. Cant recall if it was lean or rich. Banks 1 and 2Mechanic stated I would need to replace both upstream O2 sensors. He said first I could try putting in a new air filter ($20) and cleaning the throttle body ($7 carb/throttle body cleaner) before spending $55 per O2 sensor.I did this the same day and on the trip to work the check engine light remained on. Started up to head home 8 hours later and check engine light was off. Off during this mornings run.​​​​​​​Hoping cleaner air flow helped/solved the issue.