Ever since General Horse and Bull had been racing, using Magic Oil as fuel, they have created and spread Dark Exhaust all over parts of the Wild Waste. To anyone who breaths it, its just a fowl stench much like smoke. But it that a different effect on the cactus, turning them into dark cactus. Purple versions of cactus which spread rapidly across the canyon damaging or killing anyone unlucky enough to get caught. Kutaro and Pikarina had a run-in with the dark cactus, being chased up the canyon also caused by Bull and Horse, But eventually escaping its grasp and sealing it under rockslides and canyon walls. Once Kutaro destroyed General Horse and Bull's Cars, it put in end to the Dark Exhaust it caused.