Test 4
Peak power: 338 hp @ 7200 rpm
Peak torque: 296 lb-ft @ 3700 rpm
Max power gain: 9.4 hp @ 4700 rpm
Max torque gain: 10.7 lb-ft @ 4000 rpm
3000-8000 rpm acceleration: 7.80 sec
Temperature: 76° F
Humidity: 25%

Parts: Stratmosphere/Milltek downpipes
Installation time: 1.5 hours
MSRP: $1,228

• Power gains throughout rev band
• Even throatier exhaust sound
• Great fit and finish
• 12-pound weight savings over stock

• Thanks to the cats and currency exchange rate, it's expensive

Test Notes
In most vehicles, the usual bottleneck in the exhaust are the catalytic converters. Sold through Stratmosphere, Milltek's downpipes free up this restriction with a pair of high-flow HJS cats, which on MKC's dyno showed a healthy gain throughout the rev band with no losses, peaking a 9.4 hp and 10.7 lb-ft gain in the midrange. Keep in mind this is with no additional software tweaks. The sound is the best part. Whereas we got excited hearing the Magnaflow cat-back the first time, now with the two combined this RS4 truly sounds like it's got a highly tuned V8. If you can get by the price tag, Milltek downpipes are a very nice upgrade.

Test 5
Peak power: 342 @ 7500 rpm
Peak torque: 296 lb-ft @ 3700 rpm
Max power gain: 7.7 hp @ 8200 rpm
Max torque gain: 4.9 lb-ft @ 8200 rpm
3000-8000 rpm acceleration: 7.74 sec.
Temperature: 82°F
Humidity: 17%

Parts: Revo Stage 2 software
Installation time: 15 minutes
MSRP: $699

• Rev limit increased to 8500 rpm

• None

Test Notes
To make the most of the upgrades, Revo developed its Stage 2 software specifically for cars running downpipes. With this software installed, the V8's power output increased primarily in the top end, cracking the 340-whp mark and netting an additional 7.7 hp and 5.5 lb-ft at 8200 rpm over the Stage 1 software.

Keep in mind, had the Stage 2 software been compared to stock, the gain would be much larger. The rev limit has also been raised, hitting now at around 8500 rpm.

With an air filter, a header-back exhaust system and matching software, output not only rose from 321 whp to 342 whp, but there were sizeable gains from 3000 rpm through redline, making it a much better performer all around.

With all four upgrades combined, the low end improved to a peak 33.2 lb-ft of torque at 3700 rpm, and the top end to 28.2 whp at 8000 rpm, with no losses anywhere. Despite warm test weather, the measured 3000-8000rpm dyno pulls improved by 0.64 seconds and the car is significantly more responsive.

The new rumble out of the tail pipes makes the factory Sport-enabled exhaust note sound meek by comparison, and the fact that the exhaust upgrades saved 50-plus pounds definitely won't hurt performance.

Let's not forget the reduced rolling mass and improved grip. An 8 percent improvement in braking distances from 100 mph equates to a couple of car lengths.

It's not always easy improving on perfection. In fact, it's easy to make things much worse. But by choosing quality performance upgrades that actually work, it can be done. We did it here, and the owner once again is as excited as the day he drove the car off the showroom floor.

1368 Anderson Rd.
MI  48017
Revo Technik USA
5306 Palmero Court
Suite I
GA  30518
Sparkplugs.com (Monarch Products)
30500 Garbani Rd.
CA  92584
Modified By KC
6138 Merriam Drive
KS  66203
K&N Engineering
1455 Citrus Street
CA  92507
MagnaFlow Performance Exhaust
22961 Arroyo Vista
Rancho Santa Margarita
CA  92688
Continental Tires
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