With the exception of carberry, racerom etc......which have been developed to add additional maps/pub talk features, the 'code' running in an ecutek map and open source map is still the subaru developed 'running code'.
If you were to take all the tuning maps from an ecutek flashed/licensed ecu and paste them into an open source tool then flash the same car/ecu they would perform identically and vica versa.
At the end of the day its just a look up table. The ecu contains many of these tables of different resolution that the 'running code' uses.The key is to get all of the tables 'mapped' accross to work with each other. Hence the term mapping. The tuner is not re-writting the running code.
Doing a byte by byte comparison on an ecutek map, open source map or even a prodrive map would confirm that they are based on standard ROM images with just the maps, limits and diagnostic trouble codes modified.
The reason for smother afr in you example is solely down to the accuracy of the map (not the tool used to define the parameters), the position of the lambda in the exhaust vortex, the airflow through and over the car and the age/speed of the afr probe being used.
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