hey guys.. the body of my exhaust.. middle part, there's a yellowish..brownish.. something like a burn mark.. is that normal?

I can hear something like a hissing sound from the back wheels when I start my engine.. is that normal?

Also, I don't have a severe kluk..kluk.. sound on my back wheels.. should I still go to replace the bump stopper? any advantage of the newer ones compared to the stock ones?