Hey Niz, I ceramic coated my 98+ headers on my 97 car, and coated the entire exhaust, cats included, inside and out, all the way to the back muffler.
If you do it, be sure and add the OEM header blankets over the headers, there has still been some fire action on coated cars, ask the Wizard and he shall vouch!!
Heat is dropped big time, well worth the price of admission, I had a local shop do the coating for half the price of jet hot, and saved some bucks by skipping the polishing on everything other than the headers as it's covered under the sills anyways, I think around $300 US for headers to rear muffler from a shop in Michigan.
Good luck,