I play with my 3490 and convert it to 3790.
On original 3490 i have 3-5m accuracy, when i convert it to 3790 i have 7-15m accuracy.
Then i convert back to 3490 and still 7-15m accuracy.
Then i go in satellite page and add finger for 5sec on height and set Predicted EPH and cold start.
Turn off nuvi and on again and whait for satellite and after 2 min i have 3m accuracy with 7 satellite bar.