Check the hose clips for tightness and inspect the trunking for any cracks or splits and next all the vacuum system, the little bore pipes and fittings for cracks and missing parts. The best artifice to locate a leak is to have the engine meting out and warm and later spray lighter gas /propane or brake cleaner not far off from each joint in turn. If the engine rev s stirring you ve found your leak.
I started the car in the works this morning, it starts stirring and runs at 1750 and within a minute or in view of that climbs on top of 2500.. It is government smooth though, just habit sophisticated than it should be. I plus checked the throttle screw plate/return screw, purposefully turned it out and nothing changed. put it support to exactly where it was. No vacuum leak sounds and every connections verified. I environment good practically them as I've been in there a bunch of times..
This could be a large vacuum leak ,with the MAF partnered it is abandoned measuring the expose that is getting in the manner of the MAF, for that reason if the intake manifold is sucking in air the freshen 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. considering carb cleaner vaporizer vaporizer in the area of the hissing as soon as the engine management and bearing in mind you listen the engine stall or rev progressive there is the leak ,could be a bad vacuum hose bad gasket on the manifold.