Heck, that's one of the reasons I put headers on my car. Couldn't see the sense of cast iron manifolds that would rust. Jet Hot coated stainless steel looks MUCH better! Definite BLING! factor here.
I guess anything along the lines of Naval Jelly would remove the rust, but it would just be temporary. You would then need to paint the manifolds with a high temp paint to keep the rust from coming back.
Probably one alternative would be to pull off the headers and send them off to be Jet Hot coated. But heck, if you're going through all that trouble, stainless steel headers would be the better route to take, I think.
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