"Alot of people say that in order to add more fuel to an engine with a turbocharger or supercharger you need to install an FMU. A device that is similar in design to a fuel pressure regulator but adds more fuel for every pound of boost you have. This is good because your engine won't run lean and won't suffer the concecuences of detonation, but more fuel isn't necesarily the best option. What people don't sometimes know is that too much fuel is also a bad thing, it can cause overheating of the combustion chamber and will shorten the life of your turbo. That is why a programmable system makes all the difference. With a programmable system you have total control of the amount of fuel you put into the engine and also where and when need to put it in. With a programmable system you can take out fuel where it isnt needed, something the FMU can't possibly do. In order to better understand what i'm saying we need to cover the basics of the Fuel System. The main components are: the ECU, the fuel injectors controlled by the ECU, the fuel pump and the fuel pressure regulator. The ECU determines how much fuel the engine needs by calculating temperatures, the amount of air inside the engine, the throttle position, etc., then, it tells the fuel injectors to fire the necesary fuel for the mixture needed. If you install a turbocharger or a supercharger on a naturally aspirated engine, you will have to add more fuel, because the factory ECU isn't programmed for that, using an FMU will add more fuel, but it wont be in a progressive mannor, and it will most likely be too rich all the time. Properly programming the amount of fuel you need on every load point of the engine is the best way to achieve maximum horsepower, reliability and fuel economy, yes!, fuel economy, because not only can you make your engine more powerful by combining more fuel and more air to make more power, but you can also tune the areas where economoy is needed the most like idle, part throttle and cruising. You can't do any of these things with an FMU. The only justifiable reason to by an FMU is price, but then again, there are far better devices for moderate costs available."