Each powerup has a certain action index. This property is what sets the powerups behavior, and some other parameters change the effect. The list of action indexes is the same in Carmageddon and Carmageddon II, though Carma2's list has some more.
Each index has a certain number of integer and floating point parameters. If any of the required parameters is missing, the game will crash. Some indexes don't have any parameters.
1: Sets the peds' speed. For some weird reason, if the powerup number is 2 (pedestrians with greased shoes), it won't affect the speed of their movements: just the speed at which they leave their spot.
Float 6: "Force needed to trigger world exlposion"[sic]. The force needed to make it explode. 0 makes it explode on any impact, but huge values don't seem to do anything.
Float 7: Firing up vector. The force at which the mine goes up when fired.
Float 8: Firing out vector. The force at which the mine goes forward when fired.
Int 1: Direction of fire (0 - shit out, 1 - mortar fire).
Float 1: Amplitude. Sets how much the Field of View changes. If this value is too high, the camera FOV might be upside down: a common effect when increasing a game's FOV too much.
Float 2: Min period. Sets the minimum interval at which the FOV wobbles back and forth, in milliseconds.
Float 3: Max period. Sets the maximum interval.
Float 4: Impulse. This option doesn't seem to do anything.