the thing on my list would be cold air intake. extractors (a good jap brand) the cams then if you get serious pull the head off and port and polish it. play with a cam gear as you can only use 1 on the exhaust. then consider an ecu remapp from a jap tuning house,(1k or so). I have heard of 128 rwkw out of an N/A rb25.
the next and biggest step in an rb25/30 N/A I have spoken to 2 peopleabout this and they do make good power. its expensive though.
N/A is not all bad
meggala