There are many different ways that factory boost control may be set up. Typically, they are setup where the boost line to the factory wastegate actuator is tee'd off and a boost control solenoid bleeds off pressure to the intake. In this case, it will not matter where in the line you go, so you can go straight to the wastegate. If it is setup to interrupt the boost source to the wastegate, then you should get your boost-only source before the solenoid.