The main relay is a weak point on the Miata. Both age and the electrical load from high volume fuel pumps conspire to take them out. If you're lucky, it'll fail while the car is parked - it just won't wake up again. If you're unlucky, it'll fail mid-corner in a race. Yeah, we've been unlucky. A failure like that cost us the lead in Targa Newfoundland.
This kit was designed by our friends at Trackspeed and is designed to bypass the fuel pump relay. This provides an end-to-end wiring solution that is designed for higher loads, pulling power directly from the battery (or kill switch) and running it through 35A dedicated relay instead of the factory main and fuel pump relays. The harness comes pre-pinned to plug into your OEM fuel pump connector so the pump is controlled just like stock while the new mil-spec wire takes the load. Uses factory connectors and mounting points and includes a 25A fuse.
Fits all NA and NB Miatas.
A good idea on any car that needs enhanced reliability over decades-old components. A very, very good idea on cars that run upgraded fuel pumps.