This could be an airleak after the airflow meter, any ventilate dragged in here isn t seen by the ECU and fittingly not compensated for and can lean the engine out and can as a consequence permit the engine to rev taking place in imitation of not desired causing rasping running. As its a mechanical defect it tends not to point of view upon the idiosyncrasy blithe and you can sometimes listen a hissing noise in imitation of the engine running.
Its then worth getting the fuel pressure checked as if this is low due to a blocked filter or faulty regulator or even a in poor health pump will every consequences in insufficient fuel mammal delivered to the engine. Might in addition to be worth cleaning out the idle eagerness run motor / valve as these get clogged in the works like carbon and some brake cleaner washed through helps pardon things off.
have you looked into throttle body coking and/or combustion chamber/valve carbon buildup? are you taking place to date upon all maintenance; spark plugs fuel filter pcv vlave etc? have you performed a visual inspection and listened to engine as it warms stirring and is warmed up? oftentimes in engine produce an effect many factors may cause the thesame symptom(s)