I don't know anything about a miata, but these superangle rack ends are bad ass.
I don't know if you guys have heard of them, but for racing these would be great.

copy/paste from another site:

Secret Element has been in the process developing rack ends (inner tie rods) for the Miata chassis; in response to the failure of the threads on the OEM rack ends which occurs while running the Level7Tune spacers. Not only are these direct replacements for the OEM rack ends, they maximize the steering racks' travel, with 30% more travel than the Level7Tune spacers! Even if you are not exactly seeking more steering angle, chances are you current rack ends are in dire need of replacing, these fit the bill for the replacements. For those unfamiliar with the rack ends underdevelopment check out the following link http://www.roadsterdrift.com/forums/...showtopic=3420

Features:
-Direct replacement of OEM rack ends (Manual racks 90-02, Power racks 90-97)
-High strength forged 4140 chromoly steel ball joint stud
-High strength forged 4118 chromoly steel ball joint housing
-Polished ball stud and nylon race for improved wear resistance
-Black print coat for corrosion resistance
-Longer outer tie rod end threading for wider range of toe adjustment
-Steering rack travel increased 7% over OEM travel

These achieved 9 degree increase in steering angle...

OEM

Superangle