Here is the thing, Subaru have definitely been taking it easy when ti comes to their Subaru WRX STi. Maybe it is time for them to take thing seriously now.
The thing about the Subaru WRX STi is that Subaru probably did not feel that they needed to give it an upgrade since the car was still popular despite all the minor upgrade they gave it over the last few years.
The Subaru WRX STi started out with a 300HP engine and now, it comes in with a 305hp engine. 5hp more after so many years is not that much and 305hp is way below what some of the new models like the Ford Focus RS is offering right now.
It is believed that Subaru might be fitting the 2018 Subaru WRX STi with a new engine. There were talks about them possibly offering the 2.0-liter engine that will be delivering about 323hp.