Corrected entry: When Snot Rod and the other Fast and Furious inspired cars are fooling around with Mack, the camera does a closeup shot of Snot Rod revving his engine, and you can see the throttle butterflies closing when he revs higher. They should be opening, not closing, with higher revs.
GalahadFairlight
25th Nov 2009
Correction: If you look more closely, the butterfly valves are opening when he revs. They open from the bottom upward and outward. The orange reflection/glow just makes it hard to see.