Simple Question - stock O2 sensor compatible?
 

Can i use the stock FC narrowband for more than just a hole filler? Not in the position for a Wideband so just need to know before i go and by something else incase i can still use it. actually, do i even want to use a narrow band?? car will be dyno tuned

Simple answer, dont even bother, use a regular 3 or 4 wire sensor, haltech manual shows how to wire it into the harness, the single wire mazda sensor is unreliable at best, and depends on exhaust heat to work. The 3 and 4 wire sensors have heaters, thus allowing them to work much quicker and better, in the narrow band scheme of things.

Over all, get a wideband.