Sounds like the bad MAF caused a rich running condition that may have also fouled the O2 sensor.

Do you have a "check engine" light on?

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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