I built a street rod with a 400 chevy and had SS shorty headers and they turned colors and the owner said it was way to lean, I knew it was not so I called Keith Black and he told me that you want 1400 degrees 1in out of the port so I looked up a temp color chart for stainless and 1400 was a yellow blue if I remember right. A heavy load long pull I'm sure would be a lot hotter in the manifold.
On circle track engines I've seen temps approaching 1600F. That's basically 2 dyno pulls every lap though. I don't have much experience with forced induction, but I've heard that they can run much hotter than that (2000+f).
