I have one of those P90D w/ Range Upgrade (VIN 10xxxx) you speak of. And yes, it is/was confusing, the way they label it. Mine was an inventory car that had been in inventory for 9 months. So, by the time I bought it, there was no x85x anymore. The way the Owner Advisor explained it to me at the time was this: At that time the Model S x85x was the actual legal model package, and you could upgrade it to a x90x for a fee, but they weren't two separate model packages at that time. My insurance guy had the same issue.. When he put in my year and VIN, the x90x wasn't an option. The largest thing he had to choose from was the x85x. When they stopped selling the x85x, that's when the x90x became the actual legal model package.
From what I remember, the difference in range is due to the EPA changing how they determined range during that time period. If memory serves me right, they changed their testing procedures between when the x85x came out and when the x90x came out. The thing to remember here is that, the x90x is a larger capacity and will yield farther range with all else being equal.
The Tech Package option name was removed in the Spring of 2015 when they restructured their package options.
