Hello, I have repaired more than 30000 vehicles in my career and I obsession to question you questions back I am not there in person to stockpile facts, data, or to exam your vehicle. I may ask you to accomplish breakdown in my stead. If psychotherapy is needed and you would rather not proceed testing, I can have the funds for my best advice, Fuel pressure?
Its plus worth getting the fuel pressure checked as if this is low due to a blocked filter or faulty regulator or even a poorly pump will all upshot in insufficient fuel instinctive delivered to the engine. Might then be worth cleaning out the idle rapidity run motor / valve as these acquire clogged happening when carbon and some brake cleaner washed through helps free things off.
This could be a large vacuum leak ,with the MAF linked it is without help measuring the air that is getting bearing in mind the MAF, suitably if the intake manifold is sucking in ventilate the air 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. with carb cleaner vaporizer spray can in the area of the hissing considering the engine management and subsequently you listen the engine stall or rev highly developed there is the leak ,could be a bad vacuum hose bad gasket on the manifold.