How do i get the shine back on my 08 550FE header?

Hey Frank,
Got no idea about the twin exhaust but the twin exhaust I can help you with...my feild is specialist metal finishing:

1. Get on this site https://www.micro-surface.com/default.cfm?page_id=1 check out metal finishing kits, this product is an ultra flexible cloth backed super abrasive...in short you can hand wet sand failry quickly alomst to a full mirror shine or vaious levels of satin finish. Use it wet with a few drop of dishwashing liquid in the water....it's as easy as....you can use it to bring triple trees back to a clean new finish also, titanium, stainless, alloy, alloy / magnesium etc all the same system. you'll find a million uses for it the stuff lsts for ages...it's also good fortaking micro burr of new engine components... I found on my 520 that once the headers were done to a really bright level they were much easier to keep clean on going and required almost no work to keep em looking better than new.

2. Another way is to use the light Grey 3M scotchbrite hand pad, use it wet also withdetergent to clean and put a consistent light satin finish on the headers. but the Micro mesh is a better finish.

Hope it helps

Cheers

Pilot