GT5 for PS3, Tips for getting S class license

[RCAnismo]

Sorry, I posted the wrong title: It should be Gran Turismo 5 for PS3 not GTA4:

Ok, So I've placed third or better in every single race on this game fairly easily. I'm down to the last 2 in the S class. It seems like no matter what car I use or what set-up I can't get above 8th place.

It's probably just user error, but I was looking for tips if anyone had them on how to beat this game. It's starting to annoy me.