we haven't seen bunta's car yet because I stole it... I'm sorry, i'll return it soon
(no, really, i have a 2000 GME impreza 2.5RS, and it's blue, picture
http://www.linuxdrifter.com/images/Subaru001_small.jpg)
Anyway, back to the point, I would say that the one thing that I find different from 4th stage than the other stages is the fact that its giving more screen time to actual racing, and less to his personal life. Example, you used to go for half the show at the gas station talking to iketani or itsuki. Now, he's talking with the other racers and tuning his car.
Also, re-post any actual "why do cops not crack down on drifting in japan" or other actual racing questions now, I was a car guy before I learned of Initial D.
The cops actually have put in "speed bumps" on the exit and entry to some of the faster corners to kill any chance of going quickly around them. If you were to hit one of these 40' long sections of bumps at moderate-high speed, you'd kill your car. You can see what these actually look like if you watch the extras on the Tokyopop DVD (#5 i beileve) where they finally find where actual street racers race.
Also, cops in japan understand that some street racers are irresponsible (think you average american Honda Civic driver) and cause crashes, whereas some are more responsible, and actually take safety measures to counteract the danger (having people parked on the outside of corners, and flashing their headlights to warn of oncoming traffic, etc.).
go bunta