Hi! mate welcome to the club!....yep thats right you can't re-map the standard ecu, check to see what one you have though matey, >>passenger footwell, take the trim off along the door step, pull the carpet back, undo the bolts/nut on the plate...you'll see a 2 digit code on top of case on ecu eg:...mine says W6.., post again what you find, your boost could be anything between 11-13 psi depending on ecu...so i don't think your gauge is far out?.
don't over do it with the manual boost controler, wind it in about 1/4 turn at a time, i have mine set at 17 psi... i took it down from the 18 psi my chipped ecu is running, invest in a walbro 255 fuel pump, change your injectors for at least 440's if you can find some for your phase!.....if your happy with that then go for your new ecu and map.
have a look at you intercooler too, you have the slanty one?...either go for another upgraded top mount or front mount.
good luck,
mark