Ok so here's the beast:
1993 Toyota Pickup 22re 5 speed 195k miles

Here's the issue:
I have this annoying "tinny" metal on metal sound very much like a loose heat shield coming from the manifold area in the engine compartment. I have checked everything and am unable to locate any loose or rattling parts. It happens in neutral if you rev it to about 2500 rpms and in every gear but 5th it will rattle a bit then stop until the next gear. I have checked every heat shield, checked and torqued the manifold nuts, everything I can possibly think of... Any ideas?