There are two restricted opportunity modes coming which you can play to open these things Rocket League Items. One is a variation on Heatseeker mode played in another field, and the other is Spike Rush, which must be played on night maps.The Ecto-1 vehicle, already accessible as DLC, will be added to the Item Shop during this period.
Rocket League Prices designer Psyonix has reported that an energizing new game mode will be incidentally added to the game, beginning Thursday, April 16 until Monday, April 20.