2008 5.7 833 swap into 1969 GTX

We got the car running and driving but have noticed that when coasting to a stop in neutral the engine will die. Its a factory throttle body with a harness and computer from hotwire auto, they said that there is no idle control that can be adjusted like a LS engine and that some people start by drilling a small hole and keep up sizing it until it will let enough air through while the throttle blade is closed. Has anyone else experienced this problem?
thanks