Go to the used parts section regularly and check for question marks. For $1800 you can get a bottle of Nitrous Oxide, only for use in Drag Racing. To use it, press Y. Use wisely, as it is one-time only.

To obtain nitrous for the drag race you must be on a day ending in a 6 (26, 86, 236, etc). You must first lose a drag race at least one day before the day ending in a "6", or up to 3 days in advance (ends in "3").

Once you have lost, and it is a day ending in a "6", go to the used parts shop and the part will be all the way to the right under the "???". The part costs $1980 and you can only use it once (by pressing Y button) in a drag race.

Clear the second season then race the hatchback event. If you raced the hatchback event before doing so, you may not perform this trick correctly.

After you clear the second season buy a Civic Type R 02 and fully modify the car. Race the hatchback event and come in first.