You were seeking a way to enable the Smartphone link from the 2013 series in your 2012 series 3590, and you wished to do this by changing your unit's ID to that of a 3597 for that purpose, correct?
Neil, you absolutely right, I looking for way let my 3590 to be presented as 3597 thru BT connection, for that Smartphone Link on iPhone sew it as 'compatible' device.
But may be I misunderstood that Caty said
If you convert a 3790 to 34xx,for example, and enable features
about another features for my nuvi, because I already have it in turn (Smarphone Link) inside my 3590 and tested it with Android app. as well.
I thought that could be able just change model name only in BT register, not for all device. Now it's clear for me, and change reg 41 absolutely not convenient for me.