Hey, I just had an idea and wouldn't it be cool if GT4 had down hill races. Like the famous Akina? Then I can Do My Initial D Series Much Better. www.hostultra.com/~initialdseries
There's no confirmed track list at the moment so we have no idea. https://www.gtplanet.net/forum/showthread.php?t=43917 lists essentially everything we know about the courses to feature in GT4. Anything beyond that, we don't know.
One thing we need is for caras to go faster downhill. I don't know if they did or not in GT3. If you stopped on a hill and released the brakes, would it roll down the hill?