This is a useful video.
https://www.youtube.com/watch?v=ajqNR6hTSwEI give the headers this treatment every now and again and with patience it works although soon returns to a straw colour. The Exhaust is a much lower temperature so should retain its brightness.
Interesting in this and associated videos its suggested that header discoloration is a form of corrosion caused by poor quality steel. I have always found it a natural reaction with both chrome plating and stainless irrespective of quality, if the material is taken to sufficient temperature in air, although material quality does effect the readiness for this to happen.
The colours yellow, straw, brown, purple, blue etc. represent increasing temperature colour indication used in tempering steel to different levels after hardening.
I use this as well, but I use aluminium wheel polish as it's a bit more aggressive that the type polish he used in the video. I have stacks of old t-shirts and they do work very well as he's shown. You get the full 360 wrap around the pipe which cuts the work time down quite a bit.
