12:0:1 fuel managment unit. its a kind of boost dependant fuel pressure regulator that you tie in with you existing one. then your engine while ideling and driving normal will run off the stock regulator then in boost the fmu will run the engine in relation to boost the engine is getting. there o.k but running them for really long periods of time cam overwhelm the stock injectors and make them stick. hence after the kinks get worked out and your $$$s right you see scotty at main stream get ecu chipped,injectors and a tune to do away with the fmu and the missing link, wich is a spacer you get to confuse and cheat your map sensor into thinking its still in vacume when its seeing boost.