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- '17 CX-5 Select
And Black smoke does not always ,mean high HC's and CO's which would be a emission related and EPA regulated exhaust.
Well, black exhaust (oily or sooty) ALWAYS indicates unburnt hydrocarbons (the EPA considers emissions), even for the mysterious (that only Tribe understands) SkyActiv. The EPA standard is stated as xx% of noxious gases and xx% particulate matter, per mile driven. For a vehicle to be EPA compliant in its declared bin (and contribute to fleet avg bin) it has to spend the vast majority of a drive cycle in closed loop and not straying from stoich very far and not very often. You can burn as much fuel as you like (large displacement, high compression, turbo or super charging), but it has to remain near stoich for most of the drive cycle.
Last, on my CX-5, I've played with one factory and two OEM fresh MAF sensors, and they all differ slightly in calibration which can be measured and felt in low speed drivability. Not dramatic, but it is real. Mazda chose hot-film sensors for response speed (presumably), but these sensors are more difficult to manufacture to tight tolerances (as compared to many vehicles that use hot-wire). I noticed that in 2018 or 2019, Mazda switched MAF suppliers. Don't know why, but maybe the new supplier has better product consistency.