Hey WOG BOY!
**RB2530** explains it. I will post a pic to show you where the Solenoid is (But It's From a GTR R32... I Think R33 GTS-T's Might Be Different?) But to give you an idea.
Where it is circled in RED is, I believe is the Boost Solenoid. Inside there is whats called a Brass Boost Restictor, which can be removed to gain a Safe Factory Boost increase of about 2-3psi.
**RB2530** Might have a pic of what the R33 GTS-T one looks like.