If you're pulling your head or a complete engine, don't neglect the heater hoses. We strongly recommend cutting the old ones off, as the soft brass or aluminum hard lines are really easy to damage. This is the hose that goes from the firewall to the tube under the exhaust manifold.
Factory part NC10-61-212. Fits all NA and NB Miatas. Included in our hose and belt kit.
This is a weird looking part, it doesn't look right in the picture!