We recommend you to have read  The WRX engine before this section. It  will read better if you do.

The is area has three sections and a lead article. Engine Modification section is just a shameless come on. It discusses parts that you really do not need to buy for your engine, especially just getting started. The High Power Engines is yet another shameless come on. Here we discuss why 300+ horsepower for the street is not quite as easy as some tuning experts want you to believe. Both these sections are essential background to finally come to grips with the everyday possibilities of Stock Engine Mods section. With reasonable expectations we can offer some very satisfying power solutions that will not damage your motor nor put huge dents in your wallet

It seems their are as many different recommendations for increasing the WRX engine power as there are people selling parts. Instead of selling parts by the horsepower we are going to present three different articles that explore turbo motor tuning. We will not talk so much about power, just about tuning for what ever quality gas we run and avoiding detonation or other harmful short and long term effects. We are going to recommend not buying a lot of parts that have been traditionally thought of as essential for a turbo motor performance. As boost levels and fuel octane go up there are a couple of aftermarket parts worth considering, but not as many as tuning shops and manufacturers would want you to believe.

The Engine Modification section tells you what we feel does not really make power in a modest tuning effort. We have left the title as Engine Modification, hoping reader's are attracted by the title. The short form to understanding a turbo motor is that it is just a convenient hot gas generator for a turbine. The most important ingredient for power is good gas and the second most important ingredient is an ECU tuned to run the turbine's hot gas generator (your engine!) on this gas. Read this paragraph again. Tuning for power is almost this simple.

 In addition, there are of course, internal parts considerations, and external parts considerations for durability and improved power that we have to take into account as we build up the power. This was explained by just how different the Japanese high power STI engine versions are and why they are different from the current US WRX engine in the  Engine Commentary section. 

The second section relates some of our experience with powerful WRX engines that need 96, 98 or 100 octane to stay alive. Real, unleaded race gas of 100 octane at the pump has limited availability on the west coast, so for some of us, a properly built motor and a two different engine fuel maps is a distinct possibility. For others, we will make the case that 300hp on pump gas with long term reliability may be out of the question, unless the displacement is taken up to 2.2 or 2.5 liters.

The third article assumes that the car is only going to see standard pump gas. This can average from 91 to 93 octane and in some places I have heard 94 is sold. Just why does the WRX engine make 227hp and not 250hp like in Japan? What can we do about it? We explore some not so hard, fast rules to get to what kind of power level we should expect from our two liter pump gas engine.