Happy New Year!

Thx for info and clues.

@aekhong: my unit is 3790US HWID = 110
No success at all with changing to Sg/My 2.20 nor Sg/My 2.50
I was using RGN_Tool and turboccc instruction + some of my own trial/variations with HWID and SW versions.

According to PouchX's advice I've downgraded to 2.50 US (it was my one and only success ) but again i was unable to change from US to Sg/My.

Unfortunately I have to travel in next few days (Poland -Norway) by car, so i have no time (don't want to brick my Nuvi too) and i will hold up "digging" for now.

Anyway, it will be great test for my 3790

Maybe someone will find solution until I will try again