hammerstone06

First off the vehicle is a 1994 Trans AM LT1 6 speed and is bone stock. The problem is that when i come to stops the idle always drops to 500 or below, sometimes even dieing, and when the car is completely stopped and the forward momentum ends, the idle will then go back to around 800 or normal. What could cause this? also sometimes when i start it up the idle will hover around 500.