My experience with the Metro is very limited, but I've lots with some other cars that also went from Mech -> Elec on the distributor. And, the ones I know about, the swap would be very very hard to do. 99% of them do indeed require you to swap the ECU over, and most of these swaps involved a lot more than just plug-n-play. I can't think of one where all of the ECU Pins even matched. Granted, the Metro might not be as complex as others, but I think you'll be doing way more work than it's really worth. The gains will most likely not justify the work.
Not the answer your looking for I'm sure, sorry I couldn't offer more help.
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