3S-GTE Power Primer
Toyota designed the 3S-GTE for racing and they made it very capable. The second generation of the engine was very conservatively configured for the MR2 Turbo to provide high reliability and meet emission requirements. The stock US version of the 91 MR2 produces 200 HP at the flywheel. With a 20% drivetrain loss that works out to around 160 horsepower at the rear wheels (160rwhp). Since the 3S-GTE is substantially toned down from the factory, it requires little effort to get 50% to 70% more power out of the engine.
This primer provides a roadmap to those wishing to enhance the performance of their 3S-GTE. It explains what I currently believe to be the best way to gain quick, reliable power. My analysis and direct experience doing many dyno runs and configurations concludes that many cars have been modified in ways that are expensive, ineffective and unreliable. I have compiled a straightforward set of modifications that, if properly applied, will get you to 250-275rwhp. Properly applied means that when I say go to the dyno and tune you need to go to the dyno and tune. Sure it costs money and you don't get a part that you can point to and show off (you do at least get a chart that you can scan in and brag about) but it will yield good, reliable power benefits and tell you if something is keeping you from making the kind of power you should be. I will also discuss how to upgrade beyond 275rwhp, which requires a lot more money and effort.
While I mention specific products in certain cases, I do not believe in spending much time agonizing over which particular intake or intercooler or exhaust to buy as long as it meets the requirements specified. There is little extra power to be made by trying to find the "best" of any of these. In many cases, what is "best" at a particular stage becomes just adequate or even marginal or wrong at another, so my suggestion is to choose between products that meet the spec based on price, availability or personal preference and move on to the next stage.
Information courtesy of http://www.mrcontrols.com/