The TOP Nipple comes FROM the compressor housing of the turbo (Aluminum Side)
The BOTTOM nipple goes to the wastegate (Iron side)
The TOP line is where you're going to want to put the "T". When you put the "T" in the 3rd nipple of the "T" is going to go to your Manual Boost Controller or Electronic Boost Controller (MBC or EBC.) Once you install an MBC or EBC the bottom nipple of the watsegate Solenoid should be plugged because it isn't used. After that you follow the installation directions of the MBC or EBC
Pic of mine
This is the correct way to set up an MBC because the wastegate solenoid HAS to see boost, othe3rwise it can be bad information that the ECU sees.