*Audi S4 4.2L (B6/B7)
The assortment of software upgrades from sources such as APR, GIAC and Neuspeed optimize the timing map, allowing for increased throttle tip-in response and modest horsepower and torque gains. The reprogram also recalibrates the Electronic Pedal Control (drive-by-wire) for faster and more accurate power delivery. Chip upgrades can provide gains of 10 to 15 hp depending on the octane of fuel used. $399-$599
Neuspeed also offers a full 70mm T304 stainless steel cat-back exhaust system with an integrated H-pipe. The exhaust system is fully mandrel bent, ensuring maximum flow and the right amount of backpressure. $1,399
Alternatively, APR has designed a manifold-back, true dual exhaust system. The kit comes with a pair of flex-jointed downpipes that use high-flow metallic catalysts, replacing the four factory cats. The entire set-up produces claimed gains of 25 hp and 35 lb-ft torque. $2,199
*Audi RS6
An engine management upgrade on the twin-turbo V8 can hike peak power by 65 to 75 hp and provide torque increases of up to 110 lb-ft. Custom programming also removes the top speed governor and raises the rev limiter. Software sources include APR, GIAC, Neuspeed and Revo Technik. $899-$2,899
Additionally, APR provides a hand-built, mandrel bent stainless steel cat-back exhaust for this application. Starting at the catalysts, the system begins with dual 2.5-inch pipes continuing to the innovative center muffler. Exiting the muffler are dual three-inch pipes finished in a pair of twin-tip mufflers, giving the RS6 more breathing room, and a unique quad-tip set-up. $1,999
*Audi A8 4.2L (D3)
For Audi's big flagship, MTM of Germany (distributed domestically by Firma Hoppen Motorsport) offers a supercharger conversion with a claimed OEM fit and factory reliability. Three different power levels are offered, ranging from 420 to 450 hp. Those numbers should bring the car up to speed with the new V10-powered S8. $21,500-$31,850
*Bentley Continental GT/Flying Spur
Bentley takes an award-winning W12 engine from its parent company, VW, and makes it better by adding a pair of turbos, increasing the output from 420 hp to a little over 550. Neuspeed's chip upgrade gives it a claimed extra of 90 hp and a torque increase of 110 lb-ft on 91-octane gas. $4,995
The Cargraphic exhaust system (distributed by Road Sport Supply) is completely hand-made with mandrel-bent T304 stainless steel and features 70mm piping, Y design, and dual rear silencers. Gains of 20 hp and 20 lb-ft of torque have been claimed. $5,400
*BMW M3 (E36)
Active Autowerke offers a stage two turbo upgrade that's supposed to propel the vehicle from zero to 60 mph in under five seconds. The kit comes with everything needed to yield 359 hp and 367 lb-ft of torque at the wheels at 4500 rpm. $10,900
*BMW 330Ci (E46, 2001-2005)
When VF Engineering decided to supercharge the BMW 330Ci, the main focus was improving throttle response and increasing mid-range and top-end performance. This was done by using a Vortech V2 blower running 6 psi, plus supporting hard- and software. The result is a claimed 330 hp and 275 lb-ft of torque. $5,000
VFE also has a stage two package in development. This upgrade will offer a replacement intake manifold with an integrated air-to-water intercooler. Lower intake temperatures allow boost to be increased to around 8 to 9 psi. Price and performance gains to be determined.
*BMW M3 (E46, 2001-06)
For the current M3, Advanced Flow Engineering offers a stage two intake system. It is constructed of a special heat-blocking molded plastic that replaces the stock airbox and OEM mass airflow sensor housing, and it eliminates restrictive factory bends to produced claimed gains of 11 hp. The kit also features a high-flow air filter and unique anti-stall feature. $623
For the hot side, Evosport offers a performance header system that was designed using a `pulse tuning' process to maximize exhaust flow. These headers feature laser-cut flanges to ensure a leak-free seal. Each is coated with a dual-stage thermobaric ceramic coating to reduce radiant engine heat. $1,499