There are considerable posts on this topic particularly re Jap imports and it seems the earlier ones 93-95 more so.

I have a 94 WRX that I run on SUL only (no octane booster) and am not aware of any problems.

I am under the impression that it tends to occur at sustained high speed, i.e. 120mph+ where the ECU enrichment cannot function due to the KMH to MPH change and delimiter having been fitted.

But showing my ignorance but what does detting sound like?.

 

I have a MY95 WRX and have a lambdalink fitted... and i only run on super unleaded (optimax) and ive never (touch wood) had any problems so far, im always in the green on full boost..

Dan

 

best way to describe det is like someone shaking a tin can with pins in it, also known as knock, pinking and pinging.
if you use a good quality fuel and haven't turned the boost up the chances of det are quite low as the ECU can retard the ignition if it is detected (by the knock sensor)

hope this helps.