This could be an airleak after the airflow meter, any ventilate dragged in here isn t seen by the ECU and consequently not compensated for and can lean the engine out and can plus allow the engine to rev occurring as soon as not desired causing severe running. As its a mechanical irregularity it tends not to viewpoint upon the defect spacious and you can sometimes listen a hissing noise behind the engine running.
Its furthermore worth getting the fuel pressure checked as if this is low due to a blocked filter or faulty regulator or even a ill pump will every outcome in insufficient fuel bodily delivered to the engine. Might after that be worth cleaning out the idle readiness manage motor / valve as these get clogged going on behind carbon and some brake cleaner washed through helps free things off.
have you looked into throttle body coking and/or combustion chamber/valve carbon buildup? are you going on 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 affect many factors may cause the same symptom(s)