...as it sounds like an ignition-related issue:

How's your gas mileage...and have you pulled the plugs yet?

I'm thinking the plug wires are about due for replacement.

I'm only recalling the same situation last year when mine wouldn't pass, and I replaced plugs three times only to pull later and find them fouled. Eventually, the excessive fouling killed the O2 sensor.

Hesitation (and downright shuddering) when applying gas was another symptom.

Fresh plug wires made all the difference

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2009 ML350 (106K) - Family vehicle
2001 CLK430 Cabriolet (80K) - Wife's car
2005 BMW 645CI (138K) - My daily driver
2016 Mustang (32K) - Daughter's car