I think begi just announced that they can do reflashes, but up until very recently the miata ecu was basically locked. For a track car, you should be using a full standalone, either a ms2/ms3 or AEM. You are going to want the on the fly adjustability. And you will want to use e85 or race gas for a track car.
The three main ways of getting a solid miata track car are:
1. vvt built motor, naturally aspirated, about 160 horsepower. This is the most reliable setup, less heat, less parts, less fast :(.
2. Absurdflow turbo setup with built low compression motor. Less reliable, more expensive, need to get either all v-band parts or inconel studs. Cooling system needs to be top notch, positive is a lot more horsepower, savington now has pretty reliable 350 hp beast.
3. Rotrex kit, new to the miata track car list, There are a couple guys here running them, not positive who. These are supposed to generate less heat than a turbo, meaning better reliability, they still need a great cooling system like the turbo, and I'm not positive what are reasonable horsepower numbers for them, I think around 250-300 based on which unit you get.
For your 200-250 goals, I think the rotrex sounds great. Put a good amount of money into the cooling system, get a built block with a good flowing head, put some money into chassis stiffness, and slap some xidas on there