Please help..02 mustang GT

[motoxkid142]

When ever we drive our 02 MUstang gt it will be a normal sound till we rev it at about 3000 rpm and up. It will start makin a fast clicking nise and we cant figure out the problem. It started when we realized that there was only a lil bit of iol left in it so we went to go and get the stuff to change the oil. Well wen we were at the stop ligh some one was bout to rear end us so we jammed on the gas and then somthing popped and then it always made that clickin sound. We have had a engine flush 3 times and that didint work. We looked at it inside a lil bit. (i didnt want to take it apart past a certain point b cuz i wouldnt b able to put it together) Please help.