Topic moved. Please EliteMMGamer, don't post MM2 related topics always in the General section, that's not about Midtown Madness game series questions, thanks.
That tutorial is about how to make new races in the own city, but it can be helpful on how edit the already existing ones. Essentially is edit some numbers in some files using Windows Notepad. This whole operation is more easy using and editing
this mod. Check also
this post about the opponents and other related things.