stained stainless and chrome

[GoldOxide_imp]

All above advices are good.

Very tough maintenance as beautiful Spain is located between the Mediterranean Sea and the Atlantic Ocean, both of high salinity, 38-40 ppt and 33-37 ppt respectively.
Exhaust is getting hot and cold and salt just loves this type of catalysis.
You need more frequent chrome maintenance with adequate product to your climate, in general.
For your exhaust, I would recommend ceramic coating treatment.
Here is the link explaining what it is:

http://hightechcoatings.com/

Do your local research first. Good luck.
I think, you live close to the water line...?

(+1) on ceramic coating. I am adverse to chrome polishing, even if it is made easy.

Note, however, you will lose the chrome look for the most part.