my car came from jap with one of theses turbos fitted to the RB30 twincam that was in it.
theres turbos are an awesome little unit, i beleive there rated in between the HKS 2535 and 2540 range for power/flow rating
on the rb30 it was instantly on boost (obviously the extra capacity is a huge shove for it) and it now resides on a mates r31 with rb25 fitted and have been told its extremly nice to drive with it
id imagine it to be the perfect turbo to suit a rb25, maybe a little to big for an rb20 but would still be streetable
cheers
Adam