As you finish the game, you'll receive an SMS message from Rachel Teller,
telling you (well, that's normally what tellers do =) that you finished the
game, and that by acessing the option "World Map" from you garage, you can
re-race any event. And that's where the remaining 34% of the game can be
completed:
In any moment while you're in exploration mode, hit Esc and then choose
"Jump to Garage". In there, press right once then select "World Map". By the
new window that appears, press the left or right arrow keys to select one of
the 5 game stages. Then, press up and down to select an event. Select the
ones marked as "Not Completed", then enter them.
And this is how you race the remaining 34%! However, you may notice that
just by doing what was mentioned above will not award you with points or
cash after the end of a race. But I noticed something pretty strange, and
somewhat quite useful: if you hit Esc when inside a race, then choose to
restart and win, you'll get the cash! It was something that happened to me,
but then I confirmed with other fellow players. I wasn't really trying to
discover this; I think I just restarted because I messed up some race and
then noticed this occurance.