Bad rattle noise on v10

I just bought a used 03 f250 with the v10 and around 1500 - 2000 rpm I get a rattling noise almost like something loose. I had this problem on a 93 f150 351 that turned out to be a heat shield on the exhaust manifold but the 250 doesnt have any. Its loud and heard from both sides. Driving me crazy and I cant find it. Any sugestions please help.

I have the same sound it is in the Exhaust manifold the only why to fix it is to get headders and i am looking into getting some. ALso getting headders will make it a new beast. The reason i know is becasue my friend has the same truck as i do and it was a beast and quick.