Here is a history of the '98-'01 2.5RS Impreza from this thread: http://www.rs25.com/forums/showthread.php?t=20985
Subaru's Factory Hot Rod: Impreza 2.5RS
A few years ago, the sight of a Subaru at an autocross meant that some soccer kid's mom got lost on her way to the field. Sure, there were a few sporty Subarus in the '80s, like the turbo-infused GL10 sedan and wagons. Same with the flying wedge known as the XT and XT6 and with the space-age SVX, featuring Subaru's largest production engine to date.
Still, it wasn't until the introduction of the Legacy Turbo in 1991, born from Subaru's assault on Group A rallying, that motorsports enthusiasts had something to shout about. Names like Prodrive, 555, and Colin McRae soon found their way into idle bench-racing conversations. It wasn't long before these sound bites could be backed up, after consecutive British Rally Championship titles in 1991 and 1992, and a World Rally Championship win in the 1993 rally of New Zealand.
Hoping to build on their quick success, Subaru and Prodrive, the British-based tuning company headed by Dave Richards, utilized a new weapon in the form of the Impreza. First offered to car buyers in Japan in 1992, the Impreza replaced the staid and trusty Loyale in the United States in 1993.
The Impreza didn't bring much improvement in performance, however; the 110hp, 1.8-liter engine had to work hard to move the new car's extra weight. Subaru didn't stand a chance in the flourishing sport compact wars of the time. Worse yet, American enthusiasts drooled over copies of British road test magazines featuring comparisons of the new Impreza WRX with the Lancia Delta Integrale and Escort Cosworth. Faring quite well against these legendary rally specials, American enthusiasts could only fill their need by building 1/24th-scale models of Subaru's hottest offering to date.
A step in the right direction was made in 1995, when an optional 2.2-liter engine-as used in the Legacy-became available. Even a two-door coupe filled out the Impreza range. When optioned with just the right accessories, one could almost see oneself in a rally blue Impreza 2.2 Coupe, hustling around a gravel road, clearing tracks for would-be followers.
It was during the summer of 1997 when word of a "real" performance car from Subaru hit the streets. Word had it that a sporty version of the Impreza would be out. It wouldn't be a WRX, but it would offer more power, rally-inspired styling, and Subaru's now-legendary all-wheel-drive system (as Paul Hogan proclaimed in every television spot of the time).
Enter the 1998 Impreza 2.5RS. Featuring scoops and vents galore, a radiator intake large enough to swallow any rally photographer's camera, and a wing that would impress even at a hot import car show, Subaru finally had a car that automotive enthusiasts could get excited about.
Though certainly not a WRX with no giant top-end power rush, the 2.5-liter Impreza instead offers big hunky amounts of mid-range pulling power. Short ratios keep the driver busy, and lend a real sense of exhilaration when snipping up through the gears. The rally-inspired chassis speaks volumes on the road, soaking up large road confusions without a hint of instability.
It's that stability that makes the RS such a good base for an autocross or rallycross car; it won't take a driver long to get comfortable with the car. Unfortunately, the RS hasn't had a chance to show itself in stock-class autocrossing, with the current state of competition in G Stock, but has proven to be a winner in the hotly contested Street Touring arena. Ditto at rallycross events cropping up around the country. Box-stock RSes can compete for outright wins against genuine SCCA Pro Rally machines.
How to Spot Them
Subaru first introduced the 2.5RS in late 1997, as a 1998 model, selling less than 800 units. The easiest way to spot a '98 is to look for gold-colored, five-spoke wheels, and standard Impreza front bumper cover with small rectangular fog lights. Four colors were offered, with Brilliant Red, Rally Blue Pearl, and Midnight Black Pearl being the most popular. A very small number of Acadia Green RSes came out during the car's first month in production. Inside, '98 models have black-faced instruments pulled from the standard Impreza, but unique seats feature light gray cushions with brightly colored graphics. Under the hood, 1998 models were the only RSes to feature the DOHC engine.
Having sold less than 1,000 units in 1999, Subaru decided to add some boy-racer looks to the RS, including a new front bumper cover with large, round fog lights. The gold wheels were replaced with silver, of the same design. Also new on the outside, was the addition of two colors, Aspen White and Silverthorn Metallic-the latter proving quite popular.
Inside, new white-faced gauges matched up with racy red stitching on the leather-wrapped steering wheel and gearshift knob. Seats now used a less flashy checkerboard pattern in the cushion. The biggest mechanical change of the year consisted of the new SOHC Phase II engine.
Big news for 2000 was the introduction of the four-door RS to the lineup, whose only distinguishing exterior feature was the smaller L-grade rear spoiler. New six-spoke wheels were used throughout the broadened RS line, while a new darker Sedona Red and Blue Ridge Pearl came on board, with white, black and silver remaining popular. Inside, government-mandated child-restraint mounts make it easier to install a racing harness. Mechanically, a new air mass meter system was used, similar to that of the other 2.2-liter Imprezas.
2001 was really a carryover year for the RS, with only minor interior upgrades, such as carbon fiber dash accents offered as standard, and no major mechanical changes.