Hey, I was in a similar situation with my previous car. Had a rebuilt 02 spec C motor, GTPS01 (TD05-16G) TMIC, zaust fuel, headers,
ECU etc. Got 275hp and about 350Nm.
Fitted a FMIC, retune (Diff tuner boost up from 1.3 to 1.5) and got 308hp and 380Nm. Modded the dump and ran the turbo with no boost restriction at all (cause motor could take it)...I think it was about 1.7bar and got about 320hp and dont know what the Nm was. So, its do-able.
More boost, more fuel. Have a good chat with the tuner and they will tell you whats happening and what is holding it back.