Check the hose clips for tightness and inspect the trunking for any cracks or splits and plus all the vacuum system, the small bore pipes and fittings for cracks and missing parts. The best habit to find a leak is to have the engine supervision and hot and next vaporizer lighter gas /propane or brake cleaner approximately each joint in turn. If the engine rev s happening you ve found your leak.
Its along with 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 all consequences in insufficient fuel creature delivered to the engine. Might after that be worth cleaning out the idle promptness rule motor / valve as these get clogged stirring once carbon and some brake cleaner washed through helps clear things off.
This could be a large vacuum leak ,with the MAF amalgamated it is abandoned measuring the freshen that is getting in imitation of the MAF, consequently if the intake manifold is sucking in ventilate the expose to fuel ratio will be entirely 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 area of the hissing in imitation of the engine organization and taking into account you hear the engine stall or rev sophisticated there is the leak ,could be a bad vacuum hose bad gasket upon the manifold.