Yeah the sounds are not exactly great but are passable. But I do think the backfire sounds do need some improvement and it happens to often (drive the Lancer and the Mini you will understand). If they increase the sound of the exhaust note and maybe fine tune the turbo wine and just add a low hum of the engine I think it will sound good.
Also a very small detail why don't some of the cars have mudflaps? no mudflaps = penalty points lol.