Isn't "Mazdaspeed" just a trim level of a standard Mazda Miata? We don't want to get too deep into the various marketing efforts from the different manufacturers. I think this is probably something that you could add to the description of your car, but we don't want to create a new public branch of Miata for it.
We want to keep all models together. That's why we don't have different model lines for diesels vs. gas. We have filtering tools that allow you to filter some options.
On the other hand, we don't track every distinct difference between different trim levels of the same model. This is a deliberate choice to keep the "Add a Car" form from looking like an airplane cockpit. We built Fuelly for casual car drivers, not car enthusiasts. We know that turns off car enthusiasts who want to track every difference down to the details.