OK, I've just double confirmed with my mech regarding the SVT. That SEG I mentioned originally had an A/T SVT, then someone probably changed the gearbox to manual. That's why when it came to the workshop, it had a manual gearbox but an A/T ECU on it. Or.... maybe some smart ass mech changed the wrong ECU when its original malfunctioned.
However, to what I know is; the ECUs are interchangable (plug & play coz sockets are the same) & both will start & run lor. Efficiency wise, no idea.