Steve,
The NCRS guys are all over this subject. Yes, I suspect
every new car arrived with lightly rusted exhaust manifolds.
Hell, if you glass bead them and leave them out anywhere
other than the desert, they will rust almost immediately.
Jerry MacNeish seems to get a lot of notice with the Vette
crowd concerning the exhaust manifold treatment. I myself
cannot bare to see my exhaust manifolds rusted. So, Jerry
will end up doing mine soon.
Steve