i did a 1:23.880 yesterday. all i do for car setups is be simple. first i look at the track, and see what i need(top speed, or good grip). at a track like imola, u obviously need good grip. so u experiment with wing angles at about 13/14/15 degrees. then u go out onto the track and watch your gears. then change your gear ratios so that it revs high (but not too high to benefit from sstream in the race) in 6th gear, and judge where u need good acceleration. u can gain a lot of time by accel. out of the hairpin, since u judged it was very unstable in that corner. so u lower your first 2 gears to suit betta accel, then u adjust the rest of the gears so that it is smooth sailing to the sixth gear ratio that u chose. go back onto the track and practise braking late. this will show u whether u have under/oversteer, while also giving u track practise at braking late. then u analyse what felt wrong. for example, if u felt that it was understeering a bit and was very unstable when riding kerbs, then u soften the springs at the front by one increment (i dont know how large it is). u go out, and it seems problem solved, but now u are understeering into the corner and oversteering out of it. then u think "holy @!#$ what the f@# do i do now" (haha). to counter the out-of-corner problems, soften the rear anti-roll bar. if u are still understeering, THEN ONLY NOW do u change the braking ratios (ie move 1 or 2 increments to the rear if understeering).
this should be all that u change (oh yeah, also raise the ride height - front and rear - by one mm). if the car still doesnt feel good, dont mess with the other things, just try and get it right with the basic stuff. this is because u shouldnt rely on car setups to get u fastest times. THE DRIVER does that, and a good driver gets on top of the leaderboard by adjusting his driving style to the car setup, not the other way round.