Today I discovered the "missing" Daytona USA 2 textures. It turns out that these particular polygons were being misinterpreted. Supermodel thinks they are supposed to be flat shaded (because the texture enable bit is clear). A proper fix will take some time. I need to discover exactly how texture mapping is enabled or disabled. The current method is correct for all other non-textured polygons I've encountered (and there are actually quite a lot of these).
If you look closely, you can see that these polygons also store two different sets of graphics, which can be selected by some bits in the polygon header that are not fully understood yet. They appear to be stored as two or four interleaved planes of grayscale data, probably with an alpha channel to modulate their color based on polygon color setting.
Excuse my driving. The objective was to get clear shots of the AI vehicles.