It was Eunos Roadster MazdaSpeed (Mazda's AMG at the time, before factory desided to buy it) B-spec, that stands for better flowing head, 256° cams (that are same as in m2 1002), mazdaspeed header and cat back (that was made by maximworks, one of best that you can buy for mx-5) and I added Fuji Racing ITB's and megasquirt DIYPNP. it gave 128hp from engine after good tune. Great to drive and love'd the sound (still miss the sound and response) but it was quite mild set up from start. As it was, I dont really think it was worth it, unless your after glory howl and the throttle response.
The MazdaSpeed B-spec is rated as 126hp as it is, so ITB's aren't really something that you should be looking for power upgrade unless you've done head, HC cams, 1mm bigger valve's and seriously good exhaust, friend of mine is running 1600cc DD/part time track car that is upgraded with better pistons, cams, headwork and exhaust and he's running 150hp on normal plennum, so ITBs are hardly worth of the money. Most of the easy power upgrade you'll enjoy will come from MegaSquirt.
Problem with Mazda mx-5 engine is that their originally ment to be FI'd so thet dont response to NA tune like 4-age or honda engines. Plus I would ad that ITB's are harder to tune than normal plenum setup as the original throttle body hadly is the problem in NA tune.
Btw, it you haven't bought a ECU, look for Reverant who writes in most of mx-5 forums, he offers self build megasquirt that includes following and has build it so that it really works out of box and big plus is that he really has great support for ECU's he has build.