im haven a problem with my mustang. when i cut throttle she'll start to idle down but when she hits 3000 rpm it'll like bog down and skip like 400 rpm and slow down relly fast anyone no whats up?

Fill in the blanks. What have you done to get this? Are you tuning and got this? If so change it back and see what happens. Are you sure the engine doesn't have any leaks? Is this while you're coasting down to a stop?