Forza Motorsport 2

Alright, this is a solution that will allow you to win every race in your first try!
The objective of this achievement is to place second in every exhibition race. There are 15 or 16 races. Your objective is to place second, not to get the fastest time in the game. This isn't Time Trials.

So with that being said, go to your career, and buy a car menu. Select an Acura RL A-Spec. This is a D 399 class car. Now go to Upgrade and select:
1. Anti-Roll Bar: Progress-Sport Anti-Roll Bar
2. Transmission: Comptech Street Transmission
3. Clutch: Street Clutch

You should be at a D 400 class now.

Now in all of the races, the computer cannot select AI opponents above your class. Do if you have a D class, the AI cannot be C class or higher. If you upgrade your Acura as I have said, you should have the most powerful engine in the D class, at around 300hp, and great handling. Although when you look at the stats, and it says you a 3.1 on acceleration, it is inaccurate. You Acura will out-accelerate any other D class car, the computer puts you against.

I won every race by margins of 6 sec. or better. You don't have to be the best driver, I went off the roads many times and still came back to win the race, do to the speed of the car.

To unlock the achievement, simply place second in every race. Remember that the objective is to be in second place, not the fastest car in the game. Your car will have a max speed on flat land of around 115mph. That makes your car a lot easier to handle then a car going 200+mph! Unlocking Silver will unlock the Bronze sub-achievement.

Okay to get this achievement you need to be in Second Place in every race of the 15 tracks on Exhibition. But why be in second when you can finish in First place in every race? If you get First Place, you'll automatically get the All Gold Arcade (35), the All Silver Arcade (25) and the All bronze Arcade (15) Achievement at the same time.
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
2)United States
3)Lexus
4) Buy the 2003 Lexus IS300 (reg price $10,500)
5)Go to:Buy upgrades
6)Engine and Power
7)Ignition
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.

Don't Forget to change the Assists On, that will make a huge difference. This is how they should be:

Assists
Suggested Line:Full
Anti-Lock Braking:ABS On
Traction:TCS On
Stability:STM On
Shifting: Automatic

I hope that I was able to Help. Best of Luck.