Discoloration of the pipes can be cleaned off with a good metal polish and the right grade of scotch-brite. A quick search brings up a few videos and articles.

Never been fond of the look of exhaust wrap myself but that's entirely subjective.

 

0000 or 00000 grade steel wool with some oven cleaner, after warming the pipes a bit. Oven cleaner is caustic so rubber gloves needed. Maybe consider media blasting followed with black powder-coat.

 

If you use oven cleaner, make sure to protect all other painted or metal surfaces from any oven cleaner overspray.

 

The top muffler looks like it had a fire in it.
I had single wall mufflers before, they turned to several colors.
The OEM pipes have a crossover.
If the A/F did not ignite in the combustion chamber, then it burned in the muffler.
My 2 cents...
Buff it out with previous comments...