Cleaning inside exhaust headers- what to use?

Hi I just asked this question on my KZ1100 post but you may not read it if you are noy interested in a KZ1100.

So a general question really. I want to clean out any deposits and crap build up inside the headers and wondered what chemical to use without damaging the chrome on the outside.
Thanks

not sure of this will help of if you intend to go this far, but I just had my header sandblasted, and I was surprised to see that they blasted the inside as well, as far as I coudl see with a flashlight was clean inside.