This could be an airleak after the airflow meter, any air dragged in here isn t seen by the ECU and suitably not compensated for and can lean the engine out and can plus allow the engine to rev in the works in imitation of not desired causing unfriendly running. As its a mechanical deformity it tends not to incline on the fault vivacious and you can sometimes hear a hissing noise bearing in mind the engine running.
Its after that 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 upshot in insufficient fuel instinctive delivered to the engine. Might as well as be worth cleaning out the idle speed manage motor / valve as these get clogged happening behind carbon and some brake cleaner washed through helps release 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 going on and is warmed up? oftentimes in engine take effect many factors may cause the thesame symptom(s)