Okay to get this achievement you need to be in First Place in every race of the 15 tracks on Exhibition.
You can race in any class that you want. For obvious reasons, the highest the class, the faster the cars, which for some people may be more difficult.
The easy way to do this is by running in Class D. I tried several cars including the Acura RLA-Spec and it worked for several races, but here is the thing with this car, the average speed of this car is very tight, meaning that if on a race, for some reason you lose control of your car and crash, it's going to be very hard for you to catch up again. When you get to the Nurburgring Nordschleife Track you'll know what I am talking about. One mistake and the other cars will pass you, and that's 20 min. of your life that you are not going to get back.
So the formula was to have the fastest car in the lowest Class and that is the Lexus IS300.
Here is what you need to do:
1)Go to Buy car
4) Buy the 2003 Lexus IS300 (reg price $10,500)
5)Go to:Buy upgrades
6)Engine and Power
8)Buy the Accel-Sport Ignition
9)Go to:Cams and Valves on the Engine and power menu and buy the Sport Cams and valves
10)Go to:Platform and Handling
11)Brakes: and buy the Stop tech-Sport Brakes
12)Anti-Roll bars: buy the hotchkis-Sport anti roll bars
13)Transmission: Buy the Lexus-Sport Transmission
14)Clutch: and buy the Center force-Race clutch
15)Driveline: and buy the Lexus Street driveline.
So there you go, do that and not only will you have a Class D 400, but also the fastest car in that class.
By getting this Achievement you will also be getting the All Silver Arcade(25) and the All bronze Arcade (15).
Don't Forget to change the Assists On, that will make a huge difference. This is how they should be:
Anti-Lock Braking:ABS On
I hope that I was able to Help. Best of Luck.