It’s the line just above the 13b printed on the front rotor housing. And just below oil filter neck. I have a black cap over it at this time. I am trying to find a boost leak with a smoke machine and it was pouring out of this hose. If it’s not supposed to be capped please let me know.

 

It looks like the line between the Oil Filler neck and the primary turbo inlet -- part of the positive crankcase ventilation system. This topic shows the other end of that hard line:

https://www.rx7club.com/3rd-generati...ne-go-1149813/