http://www.bd4s.com.au/turbo_table.htm
Rated at 420hp, a mate of mine has a 2835ProS on RB25, makes 300+rwkw. Runs a .64 exhaust housing, internal gate, very responsive
On a RB20, it might be a little laggy, but with a decent manifold, decent boost (1.5bar) and maybe a set of cams, it would probably work alright on a RB20. If I you could though, maybe try and swap to a .64 exhaust housing. Would make allot of power, thats for sure