LAS VEGAS — Auto makers know if they build it, buyers won't always come.

But add several hundred horsepower, some giant chrome wheels and a wild paint job and they will come — in droves.

Americans may be considering more sensible, fuel-efficient vehicles in the face of today's volatile gas prices, but that is not the impression at last month's annual Specialty Equipment Market Assn. show here.

The SEMA show, marking its 40th year, has grown from 14,000 sq.-ft. in 1967 to more than 1 million sq.-ft. today.

Once an industry backwater, automotive specialty equipment such as performance and appearance parts has grown to a $34 billion industry.

The booths and aisles are packed with attendees, sometimes making it difficult to walk. Show veterans speculate the turnout is bigger than last year, with more than 100,000 attendees.

And while interest in Detroit auto maker's standard products seems to be fading as their market share drops, plants close and suppliers declare bankruptcy, the crowd here drools over new high-powered versions of Ford Motor Co.'s Mustang and lavishly appointed General Motors Corp. fullsize pickups.

Buick gets into the act at SEMA for the first time ever with some tricked-out versions of its staid Lucerne sedan. Chrysler Group's 300C sedan is another favorite of tuners at the show.

Even Honda Motor Co. Ltd., which generally brags about safety and being the most fuel-efficient auto maker in America, is showing a 500-hp Element, along with a bevy of Fit subcompacts tarted up with thousands of dollars worth of special performance and appearance options.

Honda normally talks about being clean, safe and fun,” says John Mendel, senior vice president-automobile operations. “We like SEMA because it gives us a chance to play more with the fun aspect.”

Honda revealed a prototype Civic Mugen Si Sedan prepared by legendary Honda tuner Mugen, equipped with a high performance suspension, forged aluminum wheels, aerodynamic body styling and a sport exhaust system.

Plans call for production in a limited quantity of 500 units per year, Honda says. The Civic Mugen Si will be available at U.S. Honda dealers starting in spring. It will be priced at less than $30,000 and feature a full factory warranty.

The announcement coincides with the on-sale date of the new-for-'07 Civic Si Sedan, the first time “Si” performance has been available in a sedan body style.

Similar to the existing Civic Si Coupe, the Civic Si Sedan will serve as another performance halo for the Civic lineup with a 197-hp, 16-valve, DOHC 2L i-VTEC 4-cyl. engine with an 8,000 rpm redline — mated to a close-ratio, 6-speed manual transmission and a helical-type, limited slip differential.

The Civic Si Sedan officially goes on sale Nov. 1 with a starting price of $21,290, plus $595 for destination and handling.