You should search for most of your questoins and they wil be answered...but an FMU is a Fuel Management unit. In short it just raises the fuel pressure on your car a certain amount per pund of boost so that the stock injectors provide the extra fule that is needed to match the extra air form the turbo. For instance a 12:1 FMU raises your fuel pressure 12psi per 1psi of boost. Just a chepa way of getting around bigger injectors only works for up to about 7psi max and does put soem streson your fuel system..oh and you need a new fuel pump mprolly or an inline one.