You do not need to remove the chrome to have them high temp coated. A dealership I worked for sent headers and exhaust cans out all the time to have them done. Generally they were doing the silver colored "jet hot coat", but they also did the high temp black too. They would lightly media blast them to etch the surface just like bare steel/aluminum. We were sending them to a local powder coater.
I want to say that headers or cans were running around $150-175 for the polished silver and half that for black. Its been a while.
