If you're 3 seconds off "the ring" for example, sure you could look at setup. If you're 3 seconds off from a 90 second lap time, look at your line, brake points, entry and exit speeds etc and don't worry too much about setup.
Does ISI claim to have all the nascar tracks?
Anyway, I do believe there is a one or two week refund period that you can look into if you feel that you've been sold something different than advertised. :)
I honestly don't think anybody can pin point why rF2 continues to get hated on online. To say that it's the sound is wrong IMO. I've played other sims which I believe had poor sounds but never received the hate rF2 does. I really think it's just the nature of people giving reviews online and...