Check the hose clips for tightness and examine the trunking for any cracks or splits and then all the vacuum system, the small bore pipes and fittings for cracks and missing parts. The best mannerism to locate a leak is to have the engine dealing out and warm and later spray lighter gas /propane or brake cleaner concerning each joint in turn. If the engine rev s taking place you ve found your leak.
Its moreover 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 every repercussion in insufficient fuel bodily delivered to the engine. Might in addition to be worth cleaning out the idle readiness manage motor / valve as these get clogged occurring next carbon and some brake cleaner washed through helps clear things off.
This could be a large vacuum leak ,with the MAF aligned it is unaccompanied measuring the freshen that is getting taking into account the MAF, therefore if the intake manifold is sucking in air the air to fuel ratio will be certainly out and cause the engine to stall. If MAF is disconnected the engine goes into a limp measurement and lets the engine run. when carb cleaner spray can spray can in the area of the hissing subsequently the engine admin and subsequently you listen the engine stall or rev later there is the leak ,could be a bad vacuum hose bad gasket on the manifold.