This could be an airleak after the airflow meter, any ventilate dragged in here isn t seen by the ECU and so not compensated for and can lean the engine out and can plus allow the engine to rev occurring in the same way as not desired causing harsh running. As its a mechanical irregularity it tends not to point of view on the oddity open and you can sometimes listen a hissing noise similar to the engine running.
Might plus be worth checking the wiring and connector to the airflow meter for any signs of corrosion or damage. you can do a quick irregularity find if you unplug the meter and control the engine without it. if the engine condition is the similar then chances are the meter or the membership to it is faulty. Its also worth cleaning the MAF sensor wires, as they can acquire coated once dirt more than get older which then offsets the reading. Use some right to use cleaner or brake cleaner to vaporizer onto the wires to separate the dirt on no account touch the wires taking into consideration all as they are certainly fragile
have you looked into throttle body coking and/or combustion chamber/valve carbon buildup? are you occurring to date on every maintenance; spark plugs fuel filter pcv vlave etc? have you performed a visual inspection and listened to engine as it warms taking place and is warmed up? oftentimes in engine put-on many factors may cause the thesame symptom(s)