During a race, pause the game, then hold B and Select. After, pressing A will increase the "lap timeout" variable: it is one invisible to the player; however, increasing it will allow you to stay on a race as long as you need without automatic retirement.
Note: Incrementing the timeout too high will cause an automatic timeout.
At the title screen, press A, B, A, A, A, B, A, A. If done right, a sound will be heard.
After a "Game Over", enter the following code and select "Continue". Press Up(2), Down(2), Left, Right, B, A.