 Complete the following phrase:  The engine formula was changed with the 20002004 formula. The displacement was dropped down from , and the requirement for the block to be production-based was dropped. The engines also switched to 180 crankshafts, and the rev limits were adjusted from time to time. This formula was used through 2003. In 2004, in the wake of several crashes including the fatal crash of Tony Renna and the severe crash of Kenny Bräck, the displacement was reduced to 3.0-liters using the existing engine blocks to curb top speeds started from the 