I second what 91hondawagon said, if you search you'll find in these forums everything you need to know. There's a "Tunings & Settings" subforum and, within that one, you even have separate subforums for Japanese, European and American cars.
two more notes:
1 - I saw your PSN message in the morning, but didn't have time to check my own GTR settings before coming to my office. Anyway, I think they are originaly based on these:
https://www.gtplanet.net/forum/showpost.php?p=3039804&postcount=49
although, while using the Sixaxis, I felt the need to have much closer gear ratios, because I was driving in Auto and many times felt the need to downshift much sooner than what the game was allowing. I had great acceleration, but a lousy top speed. I also changed the camber settings (to greater values) and maybe some other values, I'm allways trying things with that car.
Now that I'm using the wheel (since two days ago), and manual transmission, I have been adjusting to it and also changing the gears to see if I can get just a litle more top speed.
2 - I don't think you can win 600PP Suzuka races with the GTR
against fellow GTPer's. I have been sticking to this car because I like the car and I also like to give the grids a litle more variety, while not being completely "out of contention" from the 1st half of the overall results (4th, 5th place). If you want a winning car, you'll have to look elsewhere, not stick to the GTR.
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