The original question is also valid for model W246 with engine M270, there are versions of this engine with/without CODE 920 (gasoline direct injection with stratified charge.) I do not know if CODE 920 is a customer option, or is determined by the market location - as some emission features are.
With CODE 920 the engine has a MAF sensor plus the EGR and NOX control components.
Without CODE 920 the engine has no MAF sensor or EGR and NOX control components.
This can be seen on the WIS drawing below which shows the location of the MAF sensor (B2/5) where required.
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