It's an ebay turbo kit. It's cheaper then that new..
You could get close 300hp out of an M52. You'd have to build the engine pretty serious, but not as extensive as the previous guy said. It wouldn't be basic bolts on's though.
But why? Just buy a M52, buy a used supercharger kit and be done with it. It's the cheaper route.
Or just get a Euro S50, cheaper then a S54 and a easy swap.
91 318is - M50NV (gone)
02 WRB Subaru WRX EJ207 forged, 320 AWHP stock turbo.
85 - 325
02 325i Sedan