We're big fans of LED lighting. It responds quickly, it generates almost no heat, it lasts for a long time and it uses minimal power. What's not to love?
We use LEDs from Diode Dynamics because they're the best ones we've found. They're made in the US to high standards, not just the minimum price. They've got constant-current circuitry to protect the bulbs from transients and offer a three year warranty. Even their lumen ratings are based on actual measurements instead of advertising promises. You can buy cheaper LEDs, but you can't buy better ones.
For the side markers, we have the option of amber bulbs that use your existing rear housings, or complete replacement housings that are either white or smoked when off but still light up the right color. Note that the complete housing sets are not made by Diode Dynamics and are sold in packs of four while the bulbs are sold in pairs.
The rear corner lights on an NB are not wired to illuminate from the factory, but you can splice our replacement housings into your taillight wiring if you want them to light up.
Foglights: 1999-00 cars use an H3 bulb. 2001-03 use an H1. 2004-05 use a H11. There are a few options with the H11s. The standard H11 foglights are 780 lumens and are available as cool white or yellow. If you want really bright foglights you can use the 1630 lumen headlight version of the H11 bulb.
Headlights: 1999-00 use a 9003 bulb (not currently available), 01-04 use a 9006 bulb for low beams and a 9005 bulb for high beams. Miatas built after VIN 040901 use an H7 bulb (not currently available). We use SL1 bulbs from Diode Dynamics as, again, they're the best. They're true plug and play and have a patented optical design so they work in your existing housing. On top of that, they're designed to control heat as well as possible. Not just a big heatsink, they're designed from the inside out to channel heat to the base, where a microfan dumps it. This makes them last longer than other bulbs - they've got a three year warranty. They've gone through full OE-style reliability testing. Sold in pairs. LED headlight bulbs are legal in the USA for fog light or track (off-road) use only. Not compliant with DOT / FMVSS108 and not street legal in the USA for headlights. International legality varies by country. Note: This usage regulation is not unique to Diode Dynamics bulbs. All LED bulbs from all brands, regardless of marketing claims, are prohibited from street use in halogen headlights in the USA.
If you have cruise control and you replace all of your brake lights (not tail lights), you'll need to add a resistor to keep the cruise control functioning. If you leave a single incandescent bulb, the cruise control will continue to function with no issues.
About hyperflash: the flasher in your Miata expects some resistance from the light bulbs. If that resistance isn't there, it will flash faster, like you have a blown bulb. That's a clear sign of someone who has replaced their LEDs but hasn't paid any attention to actual function. It's a little embarassing to see. The solution is to either add inline resistors (one at each turn signal bulb, an entire car would need two resistor pairs) or install an appropriate flasher (one per car). We like the second option, but it's your call. You will need one of the two in order to prevent hyperflash.