PS ---
I was TOLD that if you BARELY WARM the header --- and then liberally apply Simichrome and allow to "soak" for 3 minutes or so... then polish off... that it does a good job of removal of the gold... and it supposedly retards it's return.
The same company sells a product called BLUEAWAY... I've not tried it yet - but plan to. It's for removing bluing from exhaust... like on motorcycles... so maybe it's just the trick.
http://www.competitionchemicals.com/blueaway/