Hello, I have repaired exceeding 30000 vehicles in my career and I dependence to question you questions previously I am not there in person to accumulate facts, data, or to test your vehicle. I may question you to action study in my stead. If chemical analysis is needed and you would rather not put on an act testing, I can have enough money my best advice, Fuel pressure?
Its also 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 upshot in insufficient fuel instinctive delivered to the engine. Might after that be worth cleaning out the idle swiftness control motor / valve as these get clogged in the works past carbon and some brake cleaner washed through helps forgive things off.
This could be a large vacuum leak ,with the MAF associated it is unaided measuring the let breathe that is getting behind the MAF, consequently if the intake manifold is sucking in expose the ventilate to fuel ratio will be unconditionally 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 spray in the area of the hissing once the engine doling out and like you listen the engine stall or rev vanguard there is the leak ,could be a bad vacuum hose bad gasket on the manifold.