Here's how I have had the wastegates hooked up in my 370 forever;
Nissan 370Z Forum - phunk's Album: phunk's TT 370z - Picture
I put a vacuum manifold on the brake booster line. Notice both ports 1 and 2 for the evc are connected to the manifold. Then port 3 goes to a bulkhead on my firewall pointing down to my wastegates.
Said and done with the plastic back on :
Nissan 370Z Forum - phunk's Album: phunk's TT 370z - Picture
That's my wastegate line headed down.