Actually, your vehicle skill RAISES your top speed. I've seen ATVs keep modest pace with the Dodge for a short while so I suspect that those rides have a higher level ATV skill, at least a 3.
PSA: Vendor previews of vehicles seem to be showing 10% higher speed and boost speed than what they are. For instance, the Orange Hemi at Crystal Pond vendor said it was 33.3 and 30.8. However, after I bought it, the info pane shows 30.2 and 28.0 like the Red Hemi.
Same thing for Duni Shetaru. It shows ~10% less for speeds in my inventory than it did when I previewed on Vendor.
And it's not my Roller skill (have +8% speed and no +boost speed yet, so that doesn't explain the odd preview).
Anyway, it appears that the Red Challenger is as fast as the other Challengers, so technically people did get the fastest car.
I should note however, that the Orange Challenger does more damage (Red = 6095, Orange = 6890)... so it may be worth it, of people want to buy it.
Challenger is definitely as fast as advertised, the skill level involved with the vehicle maybe why people are passing you that or boosting, etc.
Don't be insulted because i don't wanna explain myself, i was probably joking anyway.