High idle then dies

Sounds like an intake manifold gasket leaking. Two ways to look for it are with a length of garden hose. One end in your ear, the other move around the engine compartment til you hear hissing. Or start the car with low idle setting and open a propane tank like the kind you use for brazing. Run the propane around the intake. When the ROMs go up, you've found your leaky area.