Found this while surfing the interweb. May be of some use.

[bazza2541]

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.
The Basics of Power
Power in an internal combustion engine comes from mixing the right amount of fuel with the right amount of oxygen and inert gases in the cylinders and lighting it off at just the right moment. When the air-fuel mixture burns, it heats the gaseous byproducts of combustion and inert gases present in the cylinder. This heat raises the pressure with which the gases push against the piston and produces the mechanical energy that powers the wheels.
How can we produce more power? The hotter the gases get, the harder they push against the piston and the more power is produced. There are, however, very serious limits to how hot you can allow the gases to get before they damage the engine. Tuning the air-fuel mixture to keep combustion temperatures at the optimal range to produce the most power without destroying the engine is critical. It is also important to expel exhaust gases, because any exhaust that stays from one cycle to the next effectively lowers the temperature of the combustion chamber and reduces the power produced.
The more gases are compressed inside the cylinder before they are ignited, the more power will be produced but there is a serious limit here as well because compression heats the air fuel mixture quickly and cause detonation, which is the uncontrolled explosion of the air-fuel mixture. Detonation literally goes off like a bomb inside the cylinder and can blow spark plugs apart, punch holes in piston rings, shatter ring lands (the area on the side of the piston between the top and the first compression ring) and damage rods and bearings. Detonation is an engine killer and needs to be kept in check at all times.
The more air-fuel mixture that moves through the engine in a given time, the more power is produced. There are four ways to get more air-fuel mixture to move through the engine and every one of them has been used singly or in concert to increase power. The first way is to increase the volume that is displaced between the point where the piston is all the way down (Bottom Dead Center or BDC) and the point that it is all the way up (Top Dead Center, or TDC). The sum of the volumes of every cylinder is the displacement of the engine. The stock 3S-GTE displaces 1998cc (cubic centimeters) or 121.9 cubic inches. Divide by 1728 to convert cubic inches to cubic feet. There are three ways to increase displacement. You can increase the bore of each cylinder, which is the diameter of the cylinder. You can increase the stroke of the piston, which is the distance that the piston travels from TDC to BDC. Finally, you can add more cylinders which, as you might expect, is not easy to do without moving to a completely different engine.
The second way to move more fuel-air mixture through the engine is increasing the speed at which the engine rotates. The 3S-GTE is a four stroke engine. This means that its valves open to let air into a cylinder once per ever two rotations of the crankshaft. Given that, the amount of air in cubic feet per minute (CFM) that should move through the 3S-GTE is:
CFM = (121.9 / 1728) * (RPM / 2)
For various reasons, an engine never moves exactly this much air through itself. A fancy term called Volumetric Efficiency (VE) is introduced to modify the equation to reflect how much air is actually moving through the engine:
CFM = (121.9 / 1728) * RPM / 2 * VE
One very important thing to keep in mind is that VE is not constant, but changes with RPM and engine load. Most of the time, it is approximated with a value like 0.9 or 0.95 which is the same as saying that the engine is moving 90% to 95% of the potential amount of air that it is theoretically capable of moving. This brings us to the third way to move more air-fuel mixture through the engine: improve its VE.
The fourth way to increase the the amount of air-fuel mixture that moves through the engine is to increase the density of the air-fuel mixture. There are two ways to do this. The first is to lower the temperature of the air-fuel mixture. The lower the temperature of a gas, the denser it is. The second way to raise the density of the air-fuel mixture is to increase its pressure. Normal atmospheric pressure at sea level is approximately 14.7 pounds of force per square inch (psi). Superchargers and turbochargers are the most common devices used to increase the density of the air-fuel mixture. These devices can raise the pressure of the air-fuel mixture above ambient atmospheric pressure. The difference between the pressure they produce and nominal atmospheric pressure is called boost pressure.

[ChrisW]

Put this in with 'How-to's'?