I was offered the same thing by several dealers when searching for my Tundra DC. At first they all said it would be "factory" and "dealer installed" but when pressed for the details they admitted that it would not be the exact same unit as the NAV which comes from the factory. They said it would be an aftermarket model made by the same manufacturer as OEM and that it would fit exactly and work just like OEM but that it would be a slightly different model number. I didn't like the sound of this at all so I waited and got a DC Limited with NAV already built-in. This was about 2 months ago, though, when all Tundras were hard to come by in my area and I got the only one in the region with my config. At the time my dealer couldn't get the OEM parts so they were trying to pitch me the aftermarket install just to close the deal. I am glad I waited. This may not be a problem now since stock levels are coming up in most areas, although not sure about the number of units with NAV out there...