i think Rich has done the put big turbo on std engine and got good results

for me it all depends upon how much more power you can extract from the engine over a std ecu and its driveability.

Most of the add ons that have been developed are std equipment on modern ECUs so why would you pay to have this added onto an old ECU?

I dont have a cossie anymore but i found all the options I wanted on mine were only available as add ons to the existing OEM ECU and thus were very expensive when compared to installing a modern ECU with new loom and map.