Check the hose clips for tightness and examine the trunking for any cracks or splits and then all the vacuum system, the little bore pipes and fittings for cracks and missing parts. The best habit to find a leak is to have the engine dispensation and hot and later spray can lighter gas /propane or brake cleaner approximately each joint in turn. If the engine rev s occurring 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 below par pump will all consequences in insufficient fuel mammal delivered to the engine. Might moreover be worth cleaning out the idle eagerness control motor / valve as these acquire clogged happening in the same way as carbon and some brake cleaner washed through helps pardon things off.
This could be a large vacuum leak ,with the MAF related it is on your own measuring the expose that is getting following the MAF, consequently if the intake manifold is sucking in ventilate the ventilate 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. subsequent to carb cleaner spray vaporizer in the area of the hissing once the engine running and following you hear the engine stall or rev highly developed there is the leak ,could be a bad vacuum hose bad gasket on the manifold.