Here is my automatic manual on winning any race with any car, it doesn't matter how small your engine is or how much HP you have. This is guarenteed to win any street race.
1. Buy a Honda, Hyundai, or Daihatsu. Pretty much any car with a "Huh" sound in it is fast.
2. Buy the expensive gas, and fill up your tank till it overflows. Cars like to choke on high octane. Expensive gas = Fast gas.
3. Buy Altezza tail lights. They make your car go fast.
4. Buy lots of SiR and VTEC Tuning stickers. These make your car go fast, and intimidate your opponents. (I know I would be afraid to step up to a Geo Storm SiR)

uzzled:
5. Always, Always Buy a really huge muffler, really loud too. People will be afraid to race you if they hear V10 engine sounds coming out of your cars ASS!