I just use a bit of elbow grease, The chrome bit would have to be really big to cover the area that is affected on the back of mine, plus either a dirty bit on the red of mine or a dirty bit of chrome... no difference really except something else to scrub with brasso !!
Get a Carbon Fibre exhaust/ bodywork shield,Nick Paddy at GT-R performance parts in West Sussex used to sell them for the R33 but I don`t know about the R34?Electra in Japan do many Carbon parts......Dino.......?........Anyone else.
I have the same issue on my car and it's silvers so it really shows.........only really builds up over a couple of months though so it's not a biggy. I have found a window washer liquid that comes in concentrate for that can be used for removing things such as this and tar from bodywork too. You won't get this particular one in the UK, but I'm sure there's something the same. In fact I would think most washer liquids had to be fairly friendly to bodywork !!!!!!
But this stuff brings it off easy as, just wipe it once or twice and it's gone, then make sure you cover it over with a good wax.