Edit - Been thinking about this further and obviously as your question pointed out the petrol is throttled while the diesel is not , so my first statement is incorrect! Therefore is the MAF signal used in conjunction with boost pressure signal to correct fuelling for boost variation. Funny how a simple question makes you question what you thought you understood!
I alaways assumed that as on a petrol engine the MAF measured air-mass drawn in to the engine so that the ECU could calculate the correct amount of fuel to inject . Therefore a low MAF reading would cause underfuelling & consequent loss of power.
Taking this further if the ECU sees a normal boost reading at the same time as a low (defective)MAF reading would the ECU flag an overboost code because the expected boost at that MAF reading would be lower than the actual boost being attained.
Ready to be corrected and always ready to learn
Thanks
Andy
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