Hi Aran,
thanks for the fast response.
Here's more detailed information about the sub-categories:
1st Category
Performance > Chip Tuning & Power Box > Power Box - Diesel Engines > Alfa Romeo 147
url - /alfa-romeo-147-c1070-en
2nd Category
Aerodynamics > Rieger Tuning > Alfa Romeo 147
url - /alfa-romeo-147-c234-en
3rd Category
Lighting > Tail Lights > Alfa Romeo 147
url - /alfa-romeo-147-c399-en
The url represents the name of the subcategory with it's category id and the language.
I was thinking of changing only the url, but the urls will become much much longer, and this will not help with the problem with the anchor texts and the keyword cannibalisation ...