FG F6 turbo is a 3540, same as all BA-BF turbo variants, with 0.5 cover and cast comp wheel FG xr6T has 3576, also a 0.5 cover but smaller intake ID and smaller compressor wheel than 3540, different trim etc gt3582 is dfferent again, slightly bigger (cast) comp wheel than 3540, and 0.7 cover with 4" intake gtx3582 is different from gtx3582 only in that the comp wheel is billet, rather than cast, hence lighter and able to spool quicker and harder especially up top Also believe that billet wheel has more surface area as it's machined closer to the centre than a cast wheel is. gtx3576 has 0.6 cover, also with 4" inlet, also billet comp wheel, not sure if comp wheel is different size to cast gt3576 wheel Also pulls harder up top than gt equivalent, but still spools like crazy down low, hence its god status on here I've got a 3540 with a replacement billet comp wheel...so technically a gtx3540.... work that lot out lol All should feel free to flame/correct if I have it wrong Edit: You're correct in that gt/gtx35 turbos have same turbine housing and chra Yeh you can change but then it's not apples for apples as mr marsupial dick would say