First, here is a picture of the billboard in question:
According to the WSJ, VW was using this billboard to pitch its new GTI to young, bilingual Hispanics. But it appears that the billboard got a little too much attention. Says the article, VW quickly took the billboards down in three cities after they quickly generated a firestorm in Cuban-dominated Miami. “In English, Turbo-Balls might not sound so offensive,” says Luis Perez Tolon, an instructor at Miami-Dade College who supervises a writing program for Spanish-language network, Telemundo. “But in the Spanish-speaking community, it will always have a vulgar connotation.”
Now it could very well be that this result was very much what VW had intended. If the goal is to appeal to the younger set, sometimes offending the older set is the way to do it.