What flemm means is that when you take a vehicle change pickup, a bit of vertical velocity should be applied to the vehicle, I suppose this was added in MTA:Race to prevent cars from getting stuck in the ground. When there's only one pickup this little thrust is barely noticable, but when multiple vehicle change pickups are placed on top of each other (usually different kinds else it won't work) some mappers discovered that you can 'teleport' a vehicle somewhere above.
The trick is used in many maps, especially DDs.
how could race mode be edited that this effect will work again, because it's needed for many maps...