This could be an airleak after the airflow meter, any let breathe dragged in here isn t seen by the ECU and consequently not compensated for and can lean the engine out and can after that permit the engine to rev up later than not desired causing uncompromising running. As its a mechanical deformity it tends not to direction upon the anomaly lighthearted and you can sometimes hear a hissing noise subsequent to the engine running.
Its with worth getting the fuel pressure checked as if this is low due to a blocked filter or faulty regulator or even a not a hundred percent pump will all result in insufficient fuel innate delivered to the engine. Might as a consequence be worth cleaning out the idle quickness direct motor / valve as these acquire clogged in the works subsequent to 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 stirring 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 happening and is warmed up? oftentimes in engine action many factors may cause the same symptom(s)