If you stop doing water changes, you are essentially sentencing your poor fish to death. A level of 4ppm or higher of ammonia is definitely toxic levels and will burn the fishes gills and eventually kill them. Obviously, this is inhumane and cruel. It may seem like your water changes aren't making a difference, but trust me, they are. Your tank will not finish cycling if you kill off all your fish by stopping water changes. Yes, it will take a lot of water changes to bring down those high ammonia levels, but you really need to do them. As I've said on other threads, do one huge 75-80% water change on your tank, wait an hour, measure the levels again, and depending on the levels do another huge water change until those levels get down to safe levels. (Under 1ppm). Don't give up on your fish, you're all they have to depend on. When your cycle is over, it gets a LOT easier. So hang in there.