Not tested with other fw versions by me.
I'm not sure, but I think enabling features by using xml files doesn't work with nuvi 3790. Only by patching (modifying) region 140.
The whole device memory is divided into some regions. Region 140 is a part of the whole system.
Somewhere in this forum is a topic about executing code from SD card. At this topic is explained about regions.
This this topic is here:
[Only registered and activated users can see links. ]