There is a tipical problem with the IS, specially if the catalitic converters are damaged !
The ECU doesn't read or receives a malfuction, but reduces the fuel supply to the engine, by assuming a voltage reading different from the necesary under the actual load through the O2 sensors.
That blows the engine, cuased by engine knock at mid-hi RPM's....it happend to me.
Solution:
Eliminate all 3 catalitic converters
Install a O2 simulator on the rear O2
Add all gas you need, and the ECU won't detect any "out of parameter" rich mixture needed for S/C or
turbo engines (@11:1).