What i know there is not a actually list of best tunes/cars.
I can tell you that the following cars are good for me
D class
VW golf MK2
Honda civic VTI
Peugeot 206rc
C class
Honda integra R02
Mini cooper
B class
Chevrolet cobalt SS
Ford focus ST
Mini Cooper
A class
Subaru 22 B
Subaru sti 05
Mitsubishi evo X
Acura VIS integra
Acura NSX
Audi TT
If you go to the proffesional series jou can choose a raceclass to race. Before you select a track you push the Y button. Then you see the cars and best times that are driven on each track. Also you can download tunes by some of the drivers.
NL Franky NL