ive got a buddy with a 87 5.0 and this morning he went to start it up and it idled at 2500 rpms and it doesnt go back down we let the car run for about 15 min and it stayed the same were stumped in whats going on. we checked the iac, vacuum leaks, throttle blades and idle screw, we even blocked off all ports of air including the iac, and tb so were clueless what else could cause this and what should we be looking for? thanks for the help guys!!!