Can you run more ignition advance and boost if you have an FMIC fitted?

Currently it's a slanty TMIC on an MY96 WRX STI V.2

 

Your boost will be limited by your map sensor, so you can only really run around 16 - 16.5psi.

This is fine on the standard TMIC. Althouh a larger TMIC or a FMIC will give a cooler charge air, so timing coud be advanced a touch.
If running an OE ECU this may advance itself, if it wasn't running the Max mapped advance.

FMIC are just for show IMHO until you get up around 320-350BHP. They can also induce lag due to the long pipe runs.