It is possible the GTD had the last of the EA189 engines and needed the software.
The official figure is 181hp so a reading of 177hp is easily possible on another rolling road on a different day.
The EA288 motor fitted to the
MK3 Leon is not affected by the emissions scandal.
Your car should not need any kind or remap/software update.
The two recalls I am aware of are :
1. Boost sensor - some cars had a faulty sensor but the build records couldn't identify individual engines with the faulty sensor so it was changed at service time. ( non critical issue )
2. Indicator stalk issue - again - non critical & normally fixed during a service.