Dunno if you guys know this, but stainless steel (as on the exhaust cans) is actually an alloy. Like its cousin Aluminium, surface damage can be polished out and the metal returned to a chrome-like glitter with remarkably little effort - if you know how. I used to do this stuff when I worked in the motor trade.
When I got my Skorpion, the rear can was pretty ratty - the thing was well blued, the joint had been leaking for several hundred years and the bike had been dragged along behind a horse by the looks of the deep scratches along the side. The potential cost of a nice new unit gave the missus a dose of the screaming jeebies in the kitchen (not a pretty sight I'll have you know) so, with nothing to lose, I set to with some decent quality Wet 'n Dry (forget Halfords- crap) and soap, along with some Solvol Autosol.
I started off by hand-burnishing out the scratches with 400 grade on a rubber pad (20 minutes) then smoothed off the resulting smooth-but-rough patches with 600 (10 minutes), finally finishing off all over with 1200 and soap (half an hour). This left me with a matt silver, un-blued, leakage-mark and scratch-free can (plus aching fingers - but a smug grin).
The Solvol Autosol (nothing else I've found will do) and a brisk 15 minute buff on the bench with a piece of Terry Towelling saw the stainless start to glow encouragingly .... see pics here-
A further 15 minutes the following day and I now have a seriously new-looking can that's the equal to the wife's new ER5.
HTH