The CEL light not coming on is also a clue, none of the items that are routinely checked by OBD are malfunctioning, and if MAS were not working correctly, there would have been some error related to emission logged in the OBD. Would this not be the case ? Isnt the MAS a heated wire type in this car ? Or is it a potentiometer ? Damaged potentiometers can cause dead zones and they just cant be cleaned in any way.

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Saumil S. Patel