found an answer but not as specific as i would like...
copied from http://www.achieve360points.com/foru...d.php?t=107896
11. In the Lap of… - 20G
Beat the Luxury Champ.
- After beating the city champ you will be eligible to be challenged by the champs of each vehicle class. There are 5 champs:
* The Luxury champ - he is named Lester, and he drives one of the Mercedes.
* The Tuner champ - he is named Julian, and he drives an EVO.
* The Muscle champ - he is named Marcel, and he drives an S302 I believe.
* The Motorcycle champ - he is named Oswaldo, and he drives a Ninja.
* The Exotic champ - he is named Pete, and he drives a Ford GT.
To be challenged by the champ, you must have won a certain amount of races in a particular vehicle class. It varies quite drastically for each vehicle class. It takes around 35+ wins for each class to get challenged by the champ, however it has been known to take as much as 60+ to get a challenge.
Use the same vehicle and try maxing out your rep in that vehicle class, this will usually take 35(ish) wins to do anyway. To check your rank press BACK to bring up the GPS, and it will be in the top left hand corner. The maximum rank is 5.