Boost cut on a stock ECU is about 10psi so unless your gauge is really out it sounds like it could already be chipped mate, whip it out and have a look (silver ECU not the black one), take the back off, remove the metal plate covering the biggest chip in inside and stick a pic up on here.
You would be better going to someone who really knows RST's in and out, bit risky if he gets it wrong.