"Is it STI or isn't it STI? Well, you guys can fight that out among yourselves." - Regular Car Reviews
This debate among Subaru enthusiasts is a seemingly trivial topic. Ignore the "Sexually Transmitted Infection" jokes, and you'll find that there's actually a lot of debate on what that iconic logo on a Subaru really means. The only way to really clear it up is to try to nail down facts and shake off whatever definitions enthusiasts have given what it means when a STI badge is on a Subaru. Let's give it a go!
For starters, STI stands for Subaru Tecnica International. Born from Subaru as their technical partner and racing development team in 1988, STI hit the ground running developing Subaru vehicles to push the limits. Land speed records, World Rally Championships, Isle of Man TT Challenges, and wins at the 24 hours of Nürburgring have been key victories since STI was established. From those motorsports accomplishments, STI utilized their knowledge of racing to develop performance parts and complete Subaru cars for the Japanese market. From this aspect, STI established itself as a business component of Subaru not just to sell cool cars and upgrade parts while displaying their knowledge and abilities in racing applications.
While all of this may seem straightforward, there seems to be some dispute on what "STI" means in the US. This is because of how STI was introduced to this market and the perception that owners and enthusiasts had after it finally touched down on American soil marked by the arrival of the 2004 WRX STI. Up until that point, this car only existed in other international markets. Enthusiasts who knew Subaru were modifying their Imprezas, Legacies, and Foresters as best they could to "create" vehicles like their STI-tuned counterparts across the pond. But when the WRX STI touched down, it suddenly took on the identity of "the STI". Because the motorsports and other complete cars were still absent from the US Market, the name "STI" began to stick to the only car with that badge on the trunk: the WRX STI. This is where much of the controversy stems from, but it's more than just a misunderstanding.
Many enthusiasts in the US had associated "the STI" with one car, this distinction led to a separation between cars that were and weren't to have this kind of title. Obviously, through the association, only vehicles that were originally released as the WRX STI were legitimate in most enthusiasts eyes. However, owners of other Subarus that liked the look of certain iconic parts that made the WRX STI such a sought-after vehicle started adding these to their own. Put a hood scoop and a big wing on a standard Impreza and you're pretty much guaranteed some controversy. Add a STI badge to the trunk and you're Grade-A flame bait material. While the owner may be legitimately interested in just improving the "look" of their car, others saw this as a misrepresentation of what their car actually was. Regardless of whether the intent of the owner was to simply make something look like a WRX STI or a Forester STI just by adding badges and hood scoops was to improve their car or to fool others, it can frowned upon to do so in the automotive enthusiast world.
As the STI brand grows and increases their involvement with the US Market, this idea of what it means in the US is starting to change. Part of Subaru's Prominence 2020 plan is to boost brand value by enhancing the STI Brand. As of this post in March of 2016, Subaru is already starting to phase out older SPT (Subaru Performance Tuning) parts and replace them with STI versions. There are also sport packages for the WRX and the Crosstrek that incorporate STI parts to upgrade those vehicles. The American idea of what STI is will start to shift as the products that Subaru brings to the US begin to incorporate more performance parts and complete cars to the customers. By the time Subaru has their 2020 plans in place, it's likely that we'll already have more than just the WRX getting STI treatment. Japan already has the BRZ, Forester, and Legacy versions tuned by STI, so some of those versions could be set for release in the US as part of this expansion plan.
In the end, it will still take time in the US market for people to identify "STI" with more than one car. Once more versions of complete STI cars start to hit the US market and other performance parts are added to existing Subaru vehicles, things should start to sort themselves out. Still, after over a decade of the WRX STI being the only product to wear that badge in the Subaru lineup, the debate of what STI actually is will probably still linger among enthusiasts.