One of the first and easiest ways to add performance to your Subaru WRX or STI is to modify the ECU (Engine Control Unit) programming. We're not going to change the ECU hardware, but we're going to change the programming INSIDE the factory ECU.
Our most popular solution for this -- by far -- is the Cobb AccessPort, shown here. This handy little device includes a variety of revised ECU maps, and can increase boost levels, as well as change a whole bunch of other stuff, including timing maps, rev limits, speed governors, and more. The benefits are that you get a known-quantity ECU program with proven results, and you get the most horsepower you'll probably be able to make with a certain set of modifications on the car.
The AccessPort is a useful device in its own right, and enables live ECU data display, checking and clearing engine trouble codes, easy ECU map changes, performance measurement and "virtual dyno" functions, and lots more.
Note that the AccessPort is not the only way to edit an ECU. There are other software/hardware packages that can do it. They all accomplish the same thing, which is to allow us to apply new mapping to the stock ECU programming. The important thing is that you are applying a map that you can trust -- either one that's been proven to work on other cars, or one that has been custom-calibrated by a trained expert specifically for your car.
ECU reprogramming will continue to be a key element in future upgrades, regardless of how far you take the car. Finding a qualified ECU tuning expert (like Mach V Motorsports!) is critical to maximizing the car's output at any given stage of hardware modification.
Once you have a Cobb Accessport you can safely add a high-flow intake system to your car.