Hi Bimmer! A good car to use on the Pro All Stars Races Series would be the Mazda 787B. Do an oil change and that will give it 711HP, then try these settings:
Using Medium tires :
Spring rate: 16.4f/14.8r
Ride height: 68f/r
Shock bound: 3f/r
" " Rebound: 10f/r
Camber angle: 6.2f/5.0r
Toe angle: -1.5f/-0.5r
Stabilizers: 7f/r
Brake balance: 23f/24r
Limited slip Initial: 6
" " " " " Accel: 34
" " " " " Decel: 16
Gear ratio: Level 40
Final: 3.800
Down force: .94f/118r
ASM: 6
TCS: 5
These settings should be good for all races, except @ Test Course, where the only thing you want to do is: lower the f/r downforce to it's minimum. Don't forget to re-set it prior to the next race!
Also, you will need to PIT in all the races, at about the 9th/10th lap, except at Test Course, no pit needed, just be smooth on the turns. Don't worry about the tires ...when they start to turn red.
BTW: If you want to make it easier on yourself, when you enter the Series, enter the race only when you don't see any of the top cars on list.(R390, GT1, 787B) you simply exit the series and then, re-enter, and continue doing so, untill you only see the XJ220 race car, Altezza LM, Esperante GTR1, Impreza LM, S2000 LM, in other words, none of the real competition
However, keep in mind, that everytime you enter and then exit a race, it will add one day to your "day counter"!Good luck! 👍