whats causing Bronco to stall out?

It could be many things, unfortunately and without experiencing the problem first hand or being able to do some basic diagnostic tests its hard to say. If the engine is sound (compression is good and equal in all cylinder) and the engine components are in synchronization, ten it can be fuel or ignition related or any of the electrical/electronic controls on the the engine. The idle speed is supposed to be controlled by the idle control solenoid on the throttle housing but a vacuum leak a failed fuel injector or ignition component would put the control of idle speed beyond the control of the computer in your truck. There is a company that independent auto repair shops buy their information from that the same information inexpensively to do it yourselfers. The information is year make and model specific repair procedures, service bulletins, component locations, wiring diagrams ect.... Alldata is very easy to navigate http://bit.ly/AllData_Repair_Manuals_Online They have good diagnostic strategies out lined.