Vacuum leaks are common issues. that would be a lean condition though

If the engine is REALLY rich?? the oil separator can cause that. or like you suggested, the mass air flow sensor

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Classic codes for failing MAF. You could try cleaning it with CRC MAF cleaner (Pepboys, O'Reillys, etc). Generally you need to remove the insert (sensor) from the housing to spray in the right places. DIYs online.

The risk of running with a bad MAF is overheating the catalytic convertors and their demise; and of course poor fuel economy.

Be sure to get the correct OEM BOSCH MAF.

Good luck.

All these engines need MAF replacement.

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Kent Christensen
Albuquerque
'07 GL320CDI, '10 CL550. '01 Porsche Boxster
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This vehicle is equipped with the M272 engine. It uses an entirely different engine management system than it's predecessor, the M112. MAF sensor failures are extremely rare on these engines. The most common cause for MAF fault codes, in my experience, is an incorrectly installed air filter housing or, a torn/deformed seal where the MAF sensor fits into the housing.

I've also had a handful of cases where engine oil contaminated the engine wiring harness, causing a super-rich running condition. These were all on higher mileage vehicles. Good luck.