Re: stuck on tier B

Thank you. Wiping the save and starting fresh might be the way forward, but I'd like to check some stuff first.

I assume not, but do you have the ability to purchase another car, so you can toggle between them?

Can you modify your license plate, or manually try edit body parts(rather than trying to swap the whole kit), and does that change anything?
Are you able to play in the open world and earn money that way? It doesn't sound like an especially viable way to earn enough for a car to test, but if you happen to have a bunch saved up, you might try it?