I've just finished my Most Wanted Career (ending with 79% completion) and now I'm starting the "Challenge series". One of the last messages I received before the final credits was something like "complete the bounty rap" or "Complete the challenge series" and you'll be closer to another reward. What does this mean? finishing this adds to the career or just some % in the main menu?
The challenges seem really difficult, is it worth it to finish them? (or, as the bounty rap is also an issue, is it worth completing 100% the bounty rap? )
I've also read on some forums but I didn't quite understand that there would be some kind of "most wanted black" that continues a little bit the story, and you can meet razor etc
If anything true, please tell me what you've encountered so far

You are jumping from the bridge and running from the cops and game finishes. That is the last scene Carban is sequel of the story. So expect nothing there is no other ending. :)

have you actually finished the rap sheet? the end credits clearly specify that when topped at everything in the rap sheet there is another reward
i was just wondering what happens when you get 100% at everyting, you know?

Yes, I completed and nothing happens just you are opening all cars and everything. Here is the %100 complete savegame file you can download and try it for yourself.
http://www.fileplanet.com/187591/180000/fileinfo/Need-for-Speed-Most-Wanted--100-Precent-Complete-Save-file-with-all-unlocks

what do you mean "unlocked everything", wasn't everything ok since you finished the game?
what i meant was why do you still need to finish the challenges (what is the "Another reward" they are talking about, or what happens when you make the rap sheet 100% as well. doesn't make much sense saying there is "Another reward" at the end since there wouldn't be, no? nothing prompted, nothing appeared when finished the rap sheet?
link isn't working man