Fast And Furious 4 is set somewhere between 2 Fast 2 Furious and Tokyo Drift. At the end of Tokyo Drift, Vin Diesel makes a cameo saying he knew Han. He knew Han from exactly the stunts they pull off in the beginning of 4. And the reference he makes to Tokyo is ''I hear there's a good drift scene going on over there.'' if I remember correctly, implying that this is before he discovers the art of drifting demonstrated in Tokyo Drift.