Hey,
They're called 'hi flows'. Basically they take your stock turbo, throw away the wheels and compressor cover. They put a t04 comp cover on with a new steel wheel, machine out the turbine housing to fit a bigger steel wheel and bolt it back up to the stock manifold and dump pipe. They usually cost between 1500-2100 depending on who does the work and what components they use. Better off to buy a new t3/t04 turbo that bolts up, because the stock turbine housing is small, even after machining.