Five years ago the tuner circuit was just an urban subculture, a clique of teenage and twentysomething car junkies who enjoyed tricking up their rides, usually Japanese makes like Honda, Toyota or Acura, into rad works of art. Then in May 2001, “The Fast and the Furious,” starring Vin Diesel, shined a light onto the more glamorous–and dangerous–side of their hidden world: street racing. The movie became the sleeper hit of the summer, igniting the entire tuner biz. Last year enthusiasts spent $1.5 billion on compact-car accessories, such as moldings (fenders), wings (spoilers) and lighting. That doesn’t include special wheel accessories, like rims that keep spinning after you’ve stopped (check out SprewellRacing.com–yes, the New York Knick forward). In early November, 87,000 people flooded Las Vegas for the Specialty Equipment Market Association’s (SEMA) five-day convention. “I always say, ‘This is it, I’m done.’ But then I end up going further,” says Matt Teske, who squeezed in a day at the convention between college classes. Teske bought his ‘97 Chevrolet Cavalier Z24 used for $12,000; he and his sponsors have invested more than $30,000 on it since.

The majority of tuners don’t actually street-race. (It is, of course, illegal just about everywhere there’s pavement.) But some tuners, for street-cred points, pack their trunks with nitrous-oxide systems, a.k.a. “NOS,” which deliver a turbo boost at the flip of a switch. “They’re abusing the system,” says 22-year-old Daniel Song. “I know a lot of people who are melting their engines.”

Some tuners envy Rob Tirollo, a Florida sheriff and occasional actor, whose Mitsubishi Eclipse Spyder will be featured in the next installment of “The Fast and the Furious.” Tirollo has poured more than $50,000 into his car–some of it for “gull wing” doors that open vertically, just like a Lamborghini’s. But Tirollo refuses to race. “It’s done up as a show car and I wouldn’t want to take the chance of destroying a $6,000 paint job,” he says. And for many, it’s just not a matter of ruining their cars, but the probable consequences of street racing–such as getting $1,000 tickets or, worse, getting killed. So the tuner circuit has largely turned into an esthetic competition. The current craze is for hard-to-get exterior parts. Most Japanese manufacturers produce two versions of the same car, one for the United States, one for Japan. The overseas models have different details–the taillights, say, might have bigger reflectors–making them hot commodities for tuners.

It isn’t cool, though, to just throw anything on your car. Neon, for example, is embraced only by the newbies. Among hard-core tuners, neon is… well, it’s tacky. Now, a demon-red Hyundai Tiburon with robotic-looking ground effects, euro tails and finished off with a Japanese aluminum wing? That is hot.