Steps:
1. Go to my cars and choose add cars.
2. Get a Dodge Viper.
3. Add any spoiler or body kit.
4. Add every ultimate upgrade (except transmission).
5. Add junkman parts on everything (except the transmission - leave it stock).
6. Go to custom race and choose Omega (no matter what difficulty, laps, traffic...) and choose the Viper.
7. Tune the car like that in the video.
8. Go to the wrong way and drive where I drive and go under the building and follow the route.
9. Stop when you reach the garage door in Point Camden and do the "outside of the world" glitch by hitting the door and looking back at the same time like in the video.
10. When you go through into the garage door look back again till the walls of the garage disappear.
11. Go when I go to and when the road ends go straight and floor it.
12. If everything you did right you`ll achieve 508 km/h with no problems and you`ll see Ford GT is not op as Viper in Need for Speed Most Wanted 2005. But unfortunately Viper was nerfed in NFS Carbon so Mercedes SLR McLaren and Ford GT are the the fastest - 517 km/h with SLR McLaren and 522 km/h with Ford GT did by manual, drafter and NOS. Link:    • Video  
13. Hope you enjoyed. ^^