Miata NA flow restrictor

This is a flow restrictor that normally resides between the valve cover and chrome tube. If you replaced the hose due to age, and didn't swap over the restrictor, you probably need this. Not sure if this restrictor is on the latter cars or not. It will affect your idle, so make sure to do the TEN and GND and set base idle again after installing. If you have been experiencing the dreaded idle droop, this is a good first place to look.