Eric runs a 34 on a FMIC on GC8, i run a STi TMIC with waterspray on a GD and we're making pretty much identicle pwr/trq.

Can you Verso a GC8? I think not. FMIC/Turbo mods are always going to benefit from a good tune, regardless of ECU i think. It might go alright with the std ecu, but to get the most from it you'll need aftermarket ECU options as you've mentioned, Autronic/PowerFC etc etc.

If i were buying it i would be a little worried about the AFR's.