Looking for maximum airflow through your hood? These Singular louvers were designed specifically for the Miata. They'll increase the airflow through your radiator as well as add front downforce - it's all good.
The louvers do require you to cut into your hood, of course. But there's a good reason for that. To make installation as easy as possible, they come with clear instructions and a stick-on vinyl template to ensure you position them at the lowest pressure areas. These locations were determined by actual testing for the best airflow, and Singular reports a 50% drop in underhood pressure. There are even integral Gurney flaps ahead of the louvers to add to the efficiency.
Installing the louvers under the skin of the hood takes a bit longer, but makes for a very clean look. The kit even includes rubber trim for the opening. You can also rivet them in from above, which is considerably quicker.