Hjt wrote:And also the fuel sensor, besides Mazda who would stock replacement parts>?
Bosch, NGK/NTK and NipponDenso brands are all good, I think NipponDenso was the OEM supplier. Check Repco, Supercheap, etc and ebay, but only these brands. There are some cheap and nasties out there too.
You could consider converting to 4 wire for old 1 wire NA6s. http://www.mymiata.paladinmicro.com/Miata4-WireO2.htm or just google 4 wire sensor site:miata.net
Lambda sensors generally have the same output curves too. So you can play around a bit. My next one will be a Bosch one for a BF Falcon. It's a planar type a couple of generations on from the original NA8 one, so it's cheaper, faster, more accurate and more durable but with almost identical input/output characteristics.