Hey, here is a tool I created which can mod some things for you on Forza 4. I'm not gonna go into all this detail and write 10 paragraphs, but I will updated it with whatever anyone else wants in it. Obviously Mojobojo did most of the work on all the modders that you'll see comign up in the next few days, because he decrypted it and released it open source. So thanks for that.
http://www.youtube.com/watch?v=RfX1coLR7nQ