AE86Driver,
Dude, I feel your pain! But have no fear. I'll help ya out. I've got everything out already.
Here's how to get the courses :
Win every course available with at least 2-star setting.
This will release a new course. But note : not all courses will release another course.
I take it that you are still missing the BG1 course B4, the snow course? To get this one, you have to win Myougi. Which if I remember right, is C4.
Also, you have to win the course to release the option of playing it in reverse.
As for the cars, you have to win specific courses with setting of 3-stars and higher.
I'll do this from memory :
Akina C7 : 86Mecha (Fujiwara Takumi)(obvious, ain't it? The Tofu car! It even has the cup in the cupholder!)
Akina C6 (Reverse) : 86Turbo (Akiyama Wataru's turbo Levin)
Akagi C5 : Tuned FC (Takahashi Ryouske)
Akagi C5 (Reverse) : Tuned FD (Takahashi Keisuke)
Haruna C6 : Tuned Evo III (Sudou Kyouichi)
Haruna C6 (Reverse) : Tuned Evo IV (Iwaki Seiji)
Myougi C4 : Tuned BNR32 (Nakazato Takeshi)
Myougi C4 (Reverse) : Tuned SW20 (MR2) (Kogashiwa Kai)
Nagao Pass C8 : Tuned DC2 (Integra Type R)
Nagao Pass C8 (Reverse) : Tuned EK9 (Civic Type R)
*Can't remember the names of the two 'Initial D' drivers
B4 : Tuned GC8 (Impreza Type RA)
There are two more cars, of which I don't know how to release other than waiting for them to appear :
AE85 Trueno
AE86 Levin (Takeuchi Itsuki)
Try finishing Akina with either of these! I haven't been able to! They are SO slow! 85bhp!
Here's the life saver : It will release cars every 500km at 500km intervals (500km, 1000km, 1500km).
It also seems to release courses this way as well, but I'm not sure if it is 500km, and what the interval is.
The tuned AE86 Trueno is my favourite car as well, so it's the first one I got!
But sadly, it behaves quite a bit differently from how it is in the arcade. This car is better in the arcade.
By the way, you can check out the BG2 forum I'm from here :
http://boards.gamers.com/messages/overview.asp?name=bg2
Great drivers there, and lots of tips. My nick there is Bunta666. Enjoy!