Forget the Aventador... The stats look very good, but its Overrated as i guess...
I beat near to Every Aventador with an 791 RTR-X
The best for Boost is the F1 Elite.
My personal view of the best IGC class cars:
E: Volkswagen Scirocco
D: Nissan 240SX or 200SX
C: Pontiac Solstice
B: Shelby Cobra Daytona or BMW M3 Sport Evolution
A: BMW M3 GTS
S: (S class IGCs are still too bad) HEAVY tuned Ford Mustang Boss 302 '12
(With heavy I mean FULL Ultra)
Hope my Post is helpfull