Gave a mine the weekly wash yesterday.. well in this case it was 2 weeks!
The exhausts get pretty sooted on the GTI, I often do quite a few shorter runs in the week so always give them a good clean after the wheels. However, on closer inspection there was lots of tar spots/contamination, even after such a short period of time - only got the got early July and its done 4k now.
Anyway, everything came off with a combination of clay, Autoglym tar remover and then Carbon Collective metal polish. What do people use to seal these to help keep them looking clean - maybe some wax? I do have the Carbon Collective Platinum wheels which is a ceramic type coating, that could work?