Thought this was an interesting article. In today's NYT. DRIVING: Altering Your Engine With New Chips WHEN Scott Farrell, a Coast Guard instructor in Newport News, Va., wanted a big power boost for his 1998 Volkswagen Jetta TDI, he didn't lower the suspension, install a hot camshaft or add a free-flow exhaust. Instead, he had a business-card size electronic part installed -- a so-called ''performance chip'' designed to reprogram the car's engine control module to provide more horsepower. ''It was a night-and-day difference,'' he said. Mr. Farrell is just one of an increasing number of car owners using computer chips or software downloads to get better performance from their cars. E-mechanics are reprogramming systems to overwrite factory settings and take advantage of higher-octane gasoline. That allows advanced timing, increased power, sometimes even better mileage. Steve Dinan, founder of Dinan Engineering, a maker of high-performance parts for BMW's, said he now sells more than $1 million worth of chips annually -- a significant share of what he estimates is a $20 million market. But hacking your car's electronic brain isn't always as easy as it sounds. Installing a new chip can be a daunting job for the owner who tries to do it himself. Garage operators across the country say they are seeing more cars with burned-out engines, partly because reprogrammed chips sometimes supply too much fuel and allow turbo pressure to exceed recommended limits. And even if the engine seems to be running better, it could be running dirtier and might not pass some states' emissions tests. Spencer Cox, the owner of Speedsport Tuning in Norwalk, Conn., said that he had recently towed in a Porsche 944 Turbo with $7,000 in engine damage. The owner had ''bought a chip and other performance goodies online and installed them himself,'' Mr. Cox said. ''For a week he had a big smile on his face because he gained 40 horsepower. But then it all blew up. It happens all the time.'' And in many cases, hacking the engine can void the warranty, leaving owners to pay for expensive repairs on their own. Until the late 1970's, a car's fuel-and-air mixture was regulated by the carburetor, a relatively simple device as old as the automobile itself. But today's fuel injection systems are controlled by increasingly powerful onboard computers that regulate combustion efficiency, govern fuel economy and regulate emissions to federal and state standards. In most cases, when setting up a vehicle's computer, carmakers choose conservative settings that will allow the greatest gas mileage and cut down on maintenance problems, but will not always deliver the to-the-limits performance that owners want. That makes the chips easy prey to laptop-equipped hackers and Internet entrepreneurs who promise to ''put horsepower and torque increases at your fingertips,'' as the DiabloSport Predator describes it. Ranging from $200 to $500, these devices include install-it-yourself chips, hand-held gadgets that let owners dial in their preferred specs and computer downloads of performance-enhancing software. (Perhaps inevitably, the hacker culture has also produced automotive pirates who buy legitimate chips from makers then copy the programming onto blank chips, selling the results at sharp discounts.) Playing e-mechanic is not necessarily for the novice. To get better performance out of his 1992 BMW 325i, Chris Cagnolatti of Long Beach, Calif., paid $125 for an Active Autowerke chip, then spent ''two stressful days and nights of blood, sweat and tears working on a $1,000 computer module'' before he had it installed. The result: excellent ''bang for the buck,'' he said, though he doesn't know the actual amount of his power gain. Still not satisfied, Mr. Cagnolatti is now on his third software package, and is eyeing a device for BMW's that plugs into the car's diagnostic port ''and uploads the new software in less than a minute,'' he said. Partly to combat hackers, many carmakers are using encrypted chips in new models or, like Toyota, have done away with removable memory chips altogether. That has the e-mechanics shifting strategies, either by downloading new software directly into the computer's hard drive or attaching separate electronic devices that piggyback on the factory-installed control module and override it. Some of these devices alter the ''rev limiter'' that prevents engine speed from zooming beyond the red line or remove the speed governor that limits top-end performance. Don Jolley, a production manager at Bully Dog Technologies in Aberdeen, Idaho, which makes performance parts for trucks (and sells more than 1,000 chips a month), compares some overenthusiastic e-mechanics to the rock musicians in the movie ''This Is Spinal Tap,'' who buy custom-made amplifiers because they go up to ''11'' instead of the usual ''10.'' ''They think if a little power is good, than a lot must be great,'' Mr. Jolley said. THEN there is the warranty issue. ''We don't advocate the use of third-party components like performance chips because it means we lose control of the process,'' says Kevin McCormick, the manager of sales and service communications for DaimlerChrysler. ''We don't know the standards to which other manufacturers are building their products.'' Indeed, some performance buffs adopt a ''don't ask, don't tell'' attitude regarding their warranties and reinstall stock equipment before every dealer visit. Others wait until the warranty is about to run out before changing the chips. ''It definitely creates a concern with new cars,'' said Shaun Blanco, high-performance manager at Newins Bayshore Ford in Bay Shore, N.Y. ''Do you really want to pay $25,000 for a new Mustang, which comes with a three-year, 36,000-mile bumper-to-bumper warranty, and run the risk of having Ford drop you like a bad habit?'' (Some chip makers, like Dinan, offer their own warranties.) Peter Cheuk of Daly City, Calif., is a computer technician, so installing his Upsolute chip wasn't a big deal. And he gained 18 horsepower and 70 foot pounds of torque in his modestly powered turbodiesel 1998 Volkswagen Jetta TDI. Still, he plans to return to the stock chip. He said that the problem was that, because he now drives faster, he lost 10 miles a gallon in fuel economy and, even worse, is now trailed by clouds of black smoke. ''But if it wasn't for the smoke, I'd be happy with it,'' he said.