Yeah I get about 850kms on my gasoline N62 with a full tank . Your new MAF 8s not properly built. Aftermarket crap. A lot are. Yes the MAF can severely.adjust fuel usage AND so can the intake manifold temperature sensors. If they are reading too cold then they always allow more fuel in to burn more to get engine to proper operating temp, yet in fact the engine is at Operating temp. BUT if the temp reading at MAF is low, something is wrong with that MAF or your wiring in harmess

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I swear, my cars are like a girlfriend.
Sometimes its a rough ride, sometimes its smooth motorin'.
Sometimes she doesnt like how i treat her and sometimes i dont like how she behaves.
BUT at the end of the day, she loves it when I am inside her.

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'91 850i
'05 X5 4.4i
'09 Clubman S