Geo Tracker 1996 Helppp Idle

When I start the truck and the idle goes normal and then drops down and when i step on the brake and it dies on me. HELPPPPP (ive changed new rotor and cap)

There is a recent thread on '96 Trackers dieing at idle. Take a look at those. Try letting it warm up some more before pressing either the brake or the throttle. Also check for vacuum leaks. The brakes are vacuum boosted and when pressed may be drawing off too much vacuum from an already weak system.