Turbo or power up?
In 1.2.3 turbo aura is a .mdl file. Basically model an aura and animate it to look good.
Recharge aura is just 1 sprite beeing copied all over the place and moved upwards by the particle system. Dunno its name but to change it just change the sprite. The second part of the powerup aura is a .wrl model file. Its called aura.wrl no idea how to handle those. So i suggest you try to find a tutorial using google.