OCH:
It looks like you are well equipped to make your own exhaust system from stainless.
I have bought stainless from Burns and they are a great company.....I have also bought stainless from Cone Engineering, and they make a line of stainless mufflers for motorcycles. For street use you will want to use the Quiet Core mufflers.....the others are straight through and really won't do much to keep the noise down to acceptable levels.
https://www.coneeng.com/If you want to build your own muffler that is quiet and flows great, DragBikeMike has an entire thread dedicated to building mufflers that kill the noise while keeping the flow rate up.
http://suzukisavage.com/cgi-bin/YaBB.pl?num=1609379913I have seen the factory stainless exhaust system on Ducati and BMW that turn brown - however I do have a bit of experience with stainless exhaust systems on my Honda NT700, and the stainless system was not hard to keep shiny, it just needed to be cleaned/polished once a year to keep the brown away. The same is true of the stainless system on my F800GT - I polished it 14,000 miles ago and it still looks good.....it does have a slight yellow tint but it is still shiny. I used Burns Manifold Destiny to clean it - I don't see it on the Burns Website anymore. I don't use expensive microfiber cloths for polishing - I use old socks, flannel sheets, old T-shirts, etc. Bar Keepers Friend also works fine on stainless.
https://www.youtube.com/watch?v=IM9WDK105BkI recently bought a used Akropovic stainless header for my R1200RT. It came from a GS model and it was very brown after 40,000 miles of use. I sanded and polished it and it is now very shiny, and I will attempt to keep it nice looking. I did a process called Citric Acid Passification where you mix Citric Acid to a 4-10% concentration by weight and you soak the stainless for 30 minutes and then rinse it off. The process is supposed to neutralize any impurities in the stainless that will rust or discolor it - and make the stainless more resistant to discoloration......I don't know if it helps with heat but I thought it was worth a try. I got the Citric Acid at Walmart where they have the products for canning food. So far I have only ridden about 70 miles after installing it and the weather has been cool - but it has not yet started to get any tint (I suspect it will as the miles increase and summer heat returns........or I have to sit at a long traffic light or get stuck in a traffic jam).