Now when is still 3790 is about 23 meters but we have bad weather.
I charge now battery and then i will modified it in 3490

Will report accuracy

When i will have more time i will also try to take board with GPS chip from 3490 and add it in this nuvi.
For change GPS board i must resolder wire that is visible on picture 5.

p.s.
3790 and 3490 have the same number on GPS chip.