R32 GTSt is a great car but not the best.Also applys for the R32 GT-R>
for you id get a catback exhaust 3" or something just as good,FMIC,boost controller and smack it to 11psi.
its prob the best and cheapest power gain. check out www.modyourcar.com - maybe has a .au , they are the cheapest around i suppose for FMIC.