Have you done any engine repair recently? Sounds to me like a fairly serious intake leak or a cracked intake manifold if your TB isnt open. An easy way to find a leak is to get a can of brake clean, and start spraying your intake. I would start with the gasket area where it mounts to the head. If you do happen to spray the spot where its sucking air the engine will immediatly start to bog down. Just a suggestion. Good luck!