The first three races are easy. The third one is farmable. I make around 1.3M off of it in my tuned up/down Spoon CR-Z.
The second two, funnily enough, I can't win. I'm probably just not that great of a driver, but the best I can do is be 3 or 4 seconds behind first.
I have a civic that's pretty damn light and still has a lot of HP, but I think it comes down to knowing the track well and having a superb tuning. you can pretty much do every crazy tune to an FF to get it to oversteer and it'll probably do nothing but help you in the corners.
Let me know if you get a winning tune, though, I hate having 3/5 stars.