Damn man thanks, doesn't look like the site I used back then (I'm mantaining that it was black & yellow layout lol) though it might have gone through redesigns.
Really nice of you to help out and ask for specifics!
Funnily, I'm not playing at my home, I'm playing couple times a week when I go to my brother-in-law's house, he's offering to let me bring the ps2 with me but I always decline because I'd end up playing 10hrs a day.
So that means I don't have the access to my save right now, but I just used Nissan Silvia S13 1800cc to beat the last championship in the lowest league level (beginner, right?), and I really had a hard time finding setups for that car, in the end I used a generic setup - lowest ride height possible, spring rates pretty high (maybe around 75-80%), camber like 4.0/2.0, experimented with negative front and back toe which did get some results on corner entry but the car still understeered in longer turns, and both tended to oversteer on exits or throughout more agressive turns and lose speed to drifting. Rollbars are set to 50%, bound is 4, rebound 8, don't remember where I landed in the end with LSD settings, tried different ones... Basically the car is a bit of a mess but I still managed to win the cup by buying supersofts lol.
And when I won that, I got Nissan Skyline, 4wd one, forgot the full model designation, so I'd need setups, for Silvia and for the Skyline, I figure I'll do some more search when I get to play it again

Trying to keep it casual because I have other stuff to do and I tend to forget myself when I play gt3 haha
I suppose it's all posted around here somewhere and that I didn't look well enough, so really appreciate taking the time to kindly reply to my message about a 21 year old game. Cheers!
EDIT: Yep, it was GTVault!
Found this link, that's the site I remember
A website dedicated to the Gran Turismo tuning community. Find strategies for winning races, advice and setups for the Gran Turismo games series.
web.archive.org
Would be cool if there was a dump of all the tunings somewhere...