Endurance Run
To unlock Endurance Run, go to Peach Town and locate the car that looks like the cars in Q's Factories (he is near the main area of the town). Talk to him, and he will ask where a Q's Factory is needed. If you have a Gargage in MyCity, you can tell him. He will create a Q's Factory that has Endurance Run as its race.
Endurance Run is probably the most longest race there is. It consists of 10 laps on a long course. However, you can go into an extra lane near the starting point where you will Pit-Stop (this slows you down to 60kmph though). It is also where you race President Forest, but that is only a 3-lap race. The race consists of mostly current and future inhabitants of MyCity, but also many of the regular. The other cars don't have Jet Turbines, but are still very fast, and suprisingly don't need to pit. I wouldn't recommend racing on this track without most of the higher parts. You also need to come 6th or above in Endurance Run to complete MyCity.