I'm finally going to update the NAV in my '05 SC430, from version 3.Duh up to 8.1. I'm too cheap to spend $200 at the dealer for 9.1, so I'm on the lookout for a GEN 4 Ver8.1 online. Anyway it appears that the U-code on the disk identifies which GEN the disk is, yes? Can someone take a minute and explain the Version/GEN Code mystery to me? If this has been alrready been discussed to death, a link, please? U23 = GEN4/Ver8.1? Thanks...