as the title says, need help with this vacuum line connected to the primary turbo elbow, where does it go?

 

Goes on the oil filler neck where the nipple/hose is label with an "A".

 

Since the OP's question has been answered, I'm going to jump in with another question because there's already a diagram up.

ITT - I still have the 2 stock Air bypass valves (BOV's). How can I remove those and cap them off? I'm running HKS intakes, not the Racing Suction. I have an HKS BOV attached to a greddy elbow and I don't want the original BOV's there anymore.

 

Get some furniture rubber leg covers. The are use to prevent furniture from slipping on had floors.

 

To follow up with post #2, there are two nipples on the primary turbo inlet. The other one goes to the oil metering squirters on the rotor housings.

Mazda basically was providing filtered/suctioned air (non-boost) to depressurize the crankcase and prevent leakdown into the housings after shutdown.