When Mazda adapted their existing 1.6 and 1.8 engines for the Miata, they had to make some compromises for packaging. One of those compromises was to put the thermostat at the front of the engine, which changed the cooling flow inside the engine - and not for the better. We’ve been playing with coolant reroute kits since 2001 and this is the best one we’ve seen.
All the internal passages are smooth with nicely radiused corners for best coolant flow. Compatible with EGR, so there are no emissions concerns. An extra bleed port makes it easy to get all the air out of your system, and it has extra ports for sensors. The thermostat is close to the head for quick response and the stock temperature sensor location is retained. All the important hardware is stainless steel.
Even the installation is easier than most other kits - although the EGR pipe does need some massaging to make it fit if you're retaining EGR.
Everything you need other than coolant is included. Fits all NA and NB engines.