Sorry guys, i'm wrong, i watched the boost guage today and it does drop a couple psi above about 5000-5500rpm. Time to make up a dump now.
Nismoid, its a pretty good cooler kit, the guy who makes them designed it on his stock R33 which gained 40HP at the wheels with just the cooler, standard exhaust as well. The R31 coolers are just shit, even a standard R32 cooler will probably make a difference on a R31.
Carlos