mate i have a 31 with a Rb20 in it, whuch replaced my old RB30e with a big cam , headwork, extractors, 2.5 inch exhaust etc, and the standard rb20 would kill it.
i have upgraded it bit by bit and can honestly say they are a great motor, and in no way a downgrade from a RB30e
first up put on a good 3 inch mandrel bent exhaust, second a good sized front mount cooler, and wind the boost up to 13 or 14 psi.
For not alot of money you are going to have a quick car, worthy enough to scare wrx's and 200sx's.
This is presuming you have a 5 speed. I would also suggest 4.11 diff ratio's.