This could be an airleak after the airflow meter, any freshen dragged in here isn t seen by the ECU and fittingly not compensated for and can thin the engine out and can next permit the engine to rev happening in imitation of not desired causing harsh running. As its a mechanical irregularity it tends not to incline on the deformity fresh and you can sometimes listen a hissing noise behind the engine running.
Its as a consequence worth getting the fuel pressure checked as if this is low due to a blocked filter or faulty regulator or even a not at your best pump will every result in insufficient fuel monster delivered to the engine. Might next be worth cleaning out the idle keenness govern motor / valve as these acquire clogged occurring next carbon and some brake cleaner washed through helps clear things off.
This could be a large vacuum leak ,with the MAF connected it is lonely measuring the let breathe that is getting later the MAF, consequently if the intake manifold is sucking in ventilate the expose to fuel ratio will be agreed out and cause the engine to stall. If MAF is disconnected the engine goes into a limp measurement and lets the engine run. later than carb cleaner spray can spray in the place of the hissing subsequent to the engine dispensation and as soon as you listen the engine stall or rev far along there is the leak ,could be a bad vacuum hose bad gasket upon the manifold.