Boost Valves  
The basics
If your car is equipped with electronic fuel injection a power boost valves will give you an instant increase in power. Instant, in that you will notice it as soon as you snap open the throttle, and instant, because it is a simple bolt on fitting - directly replacing your existing fuel pressure control valve.

How it works
In an electronic fuel injection system, the fuel is drawn from the tank by the fuel pump, and passed to the fuel rail for delivery to the cylinders via the injectors. Because the fuel pump sends the fuel in pulses, a fuel pressure control valve is required to stabilise the pressure in the fuel rail to provide a constant feed to the injectors. As you accelerate the demand for fuel increases.

Installing a boost valve
First things first, remove the air filter ducting and the breather hose from the oil filler cap. Then remove the electrical plug that connects to the air intake / manifold. this will give you access to the fuel rail and regulator. Next remove the clip holding the regulator in the housing and gently pry the regulator free, next fit the regulator adapter (FSE) into the housing and refit the clip that secures it. Remove the RED clip on fuel pipe - this is the return to tank feed, cut this pipe just behind the red connector, fit the union supplied into the cut off pipe, and blank off the pipe stub (on the rail) with a short length of fuel hose with the bolt in one end, clip up tightly with the supplied clips. Find a suitable location to fit the mounting bracket.Next cut a suitable lenght of fuel hose and connect it to the side pipe stub on the new valve and the pipe stub on the FSE supplied regulator adapter (secure tightly with the clips) Then connect another length of fuel hose between the bottom stub on the valve and the union that you fitted in the return to tank plastic fuel line. Lastly, fit the new vaccuum hose to the small stub on the top of the valve and the other end on the inlet manifold. Next, before testing, ensure all connections are secured tightly with the clips, and that none of the pipes foul on any other components.

The performance increase amounts to better fuel pick up and throttle response. Don't adjust the valve unless you know that it will benefit the car! The valve may need proper setting up at a performance specialist if a superchip or similar is fitted. On a scale of 1 to 5 of difficulty i would rate this as 3.
Make sure all hoses are secured and that no leaks occur.