i have seen all 3 stages for the anime, but never read the comics, anything different between the manga and the anime? or they are pretty much the same?
i read something about Bunta's impreza and carbon hook on ae86, and project D, non of these are in the anime

for the last message, i meant carbon HOOD. not hook.

i did some research, i think these things happened after the 3rd stage, and will be in the 4th stage, but im not sure though

Edit button...
These are all from the manga, I can post up a quick summary...
the 3rd stage movie deviated from the manga pretty much, you do remember Initial D is based off a manga, right? So after what happens in 3rd stage, (in the manga, Natsuki gets a job at the gas station with Takumi, not some McJob) he hooks with up Project D. They go to Shomaru? (I'm a bit rusty, havent looked at the manga in a while, you know?) Pass and race "SSR" (Seven Star Reaf, its mean to be Seven Star Leaf, but Japanese can't speak english :p) They obliderate the FD vs R34 and Roadster vs AE86 matches. (go Proj D!). Im too lazy to cover the whole story...but to answer your questions
Project D begins to tune the AE86 for Takumi, FREE! and he gets carbon fiber hood among with many other goodies. Since Takumi is out racing all night with Project D, Bunta says he will help take over some of the deliveries, and says he will transfer the title of the AE86 over to Takumi, giving him the car. :D Takumi is suprised and asked about Bunta himself, and he stated he already looked for a car. Bunta calls him his freind at the stop (remember dude who imported him the engine?) and says "I dont want anything flashy, like with a big wing" (gets one anyways..) and he sends up getting 4WD! He took it out for a drive and... One night, Takumi was making his delivery, and a black car pulled up behind him (Subaru Impreza WRX STi Type R, coool, but since Takumi is dumb, he doesnt know this) He begins to race the down hill but Takumi barely misses his countersteer and the black car flew past him (this was before the AE85 vs S15 race). Bunta called up later and said "I like it, Ill take it" :p Takumi told Itsuki later that his dad got a new car and he was like "Probably an automatic van, hes an old man now..." Hah, wasnt he suprised :p Bunta let Takumi drive the 4WD for awhile but Takumi didnt like it and took his AE86 back.. (fool!) And that answers your questions right?