Let's Go: Eternal Wings Codes -

Hidden shop:
If you finish stage 7, go up to the mountains. When you get stuck, press Circle. You will be in a new shop. Its a normal shop, but when you go to the gear ratio section you will see something worth 30,000. Its is an object that makes your car go top speed.

Hint: Final stage:
The Boss' car is a exact duplicate of your own -- know your car wisely.