bhp on stage 3 Cos can vary I've seen them to be as low as 285bhp and as high as 380 depending on who's chip and set up and what other bits you add! most would say you need at least a group A head gasket(standard will blow),also @ least a 4x4 i/cooler and a T34 turbo with 48 or 63 exhaust housing for a genuine stage 3 set

ps If do buy it you'll be better of having it set up also