Teeth is still busy moving, but should be around soon to shed some light. In the meantime I dug up this old topic from the archive: http://ssgtirep.com/tsarchive/viewtopic ... 61555.html
Here’s the interesting bit:
"Yes there are differences, however, it doesn’t matter which one you use, they will all plug and play unless you have an automatic–or a CA car with EGR, I guess.
The later ECUs, I2 (92-93) and I6 (94 only) make slightly more power, probably due to a slightly more aggressive timing map and faster processors. Unfortunately, offsetting that advantage is a bug in the code that can prevent the ECU from enrichening properly with the throttle until well after warmup–don’t try to run one of the later cars hard until you’ve been driving 15 minutes or so.
Don’t forget there are Euro-spec ECUs that are expecting input from a trim-knob rather than an O2 sensor (but will accept that too).
Even a Cultus ECU from those years will run an export-spec motor, but it wouldn’t be a good idea as the maps would not be optimal and you’d get a code for a missing knock sensor."
So still not sure what the lettering is on the 89-91 ECU, I can pull mine if needed and have a look at it. But I think I’ll be able to dig it up given just a little more time rooting around in the archives.
Admin of the Suzuki Swift Repository, as well as a GTi fanatic! Currently own a Red 89 GTi
and a Black 93 GT