have you rechecked codes since resetting to see if maf code has reappeared?
i would ditch the zerosports chip as its probably mapped for 100ron and very aggresive. no need to source another ecu, just remove chip inside and resolder resister j1, it will be the one cut.
regards overfuelling if plugs are ok, i would change lambda for universal three wire bosch one as they are not dear and being fitted in early jap location of headers its probably had a fair heat up anyway.