Hmm, you still need to deinstall the pirated version, otherwise it will not work
Fix the original Steam-Install, thats the way everything works fine.
You need to deinstall every Track vom STCC in your Locations-Folder and every Car, otherwise the Steam-Update will not work.
The game prior the data out of the Gamedata-Folder, and it will not use the updated files from your Steam-GCF's.
So still the best (at least the easiest) way is to uninstall the whole Game and install it again through steam.
To make it more clear:
You may have an outdated version of Oschersleben07-B-Course in your Gamedata folder.
The Steam-GCF includes the up2date Version of Oschersleben07-B-Course. Now if you start your game it will use the outdated version from the Gamedata-Folder. Thats causing all your trouble
By the way -> Thats the same system how our trackfix works. We have included the fixed (but same named) gdb's into the Gamedata-Folder, so the game will use our fixed files from the Gamedata-Folder and not the broken ones in the gcf-files.