Sames as the other sandbox scenario but this time there's three blackholes - all blackholes have the same pull.
To change vehicle, make sure that the scenario is not under competitive conditions (to check this, go to Options > Gameplay and uncheck Competitive Scenario Conditions). Then, simply press CTRL+E to open the vehicle menu where you can select your vehicle.
Multiple vehicles are now supported so you can have more than one vehicle affected at once.
To reduce extreme values, there is a cap as to the amount of pull the blackhole has so when your car is within a small enough range of the blackhole, the same force will be applied to the car.
Have fun!