Need help with Payback I can't level up enough.

I'm not sure if I'm doing something wrong or what the problem is but I have gotten to level 29 I think for my rep and no matter what I try all I can not unlock and upgrade cars that are fast enough to compete with the NPC cars.

For example they want me to do a Drag Race and they recommend a car with a level of 310 but the highest I can get is a car that is fully upgraded to a level 279 and it's like this for all class's and I can not compete the NPC car's at all.

I have tried going for the car's with the fastest top speed for like the first Corvette that you can unlock and after using to complete the event's that are available it is now to slow and I can not buy another car and upgrade anywhere close to what the game says I need.