I think he/she is trying to say "I have seen automatic powerstrokes make a loud metallic scrapping noise until the torque converter locks up".

Do you have a automatic? If so the torque coverter (I have read) can make noise and or the flexplate can crack and make noise.

Does it change as the motor warms up? If so it could be the 7.3 "cackle", the #8 injector somtimes will do this. Look up "cackle" to read up on it.