Where does the long hose coming out of the sub zero fluid tank run to?

 

That line runs to a large nipple on the carb that's located right between and a little below the two omp fittings.

 

Unless you're looking for a factory build, the cold start assist isn't needed. Mazda had a Technical Service Bulletin to disable it. I think they just say to unplug the pump wiring. I removed my sub-zero tank and plugged the port on the carb.

 

Didn't know about the bulletin, which is interesting by itself, but I've removed mine as well. Some carbs don't have the internal passages for the sub-zero system, so that's something to watch out for too, I think. Perhaps don't quote me, it's be a while since I looked at my carbs. I believe the system would be plumbed to exit the large, sideways hole on the AP nozzle block.