The radiator needs a few things, but lets talk about airflow, which the stock setup lacks, you have an intercooler AND an air con condenser in front of it. And behind it there isnt much of a way to release the air.
Firstly have a look into the mouth and make sure that all the front of the radiators ducting is there, so that any air that makes it through the mouth is forced through the radiator, check for gaps underneath, to the sides and on top, near the hood latch.
Block them, use coreflute, sheetmetal, expandafoam, I dont care.
Next we need a way to get air out of the engine bay. The most common way is an extraction vent in the hood just in front of the engine block i n the hood.
This location is a very low pressure zone, caused by the aeroplane wing like curvature of the front profile of the car.
This shape and hence low pressure zone causes lift, this is why the steering gets light at high speeds. An extraction vent here will actually reduce lift, increasing front grip, and it will actively pull air through your intercooler and radiator.
Search mini hood scoop miata. By mini I mean the car made by bmw, their hood scoop is purchased, turned backwards so as to be an extraction vent, and fits the mx5 perfectly in the location I mentioned.
Or use whatever scoop, but it needs to be backwards and used for extraction.
Looking for unripped NA door trims, thanks.
Side effects may include Gratuitous Amounts Of Horsepower.
F#ck your fake performance.