The turbo won't do much with no vacuum on the wastegate. Sounds like the wiring to the solenoid. Look right where the wires enter the plug. They often break there.
You said 15" teed into the line after the solenoid; this implies the solenoid and its associated circuitry is working. If it is, you should have vacuum on the wastegate at least up to about 1800RPM. The PCM will not disable it at lower RPM's. If you're getting zero at idle that points to an intermittent wiring fault or loss of vacuum source.
Any DTC codes stored? I'd expect DTC-78.
Also, make sure the vacuum pump is connected to the port on the solenoid with the restrictor in it.
The Constitution needs to be re-read, not re-written!
If you can't handle Dr. Seuss, how will you handle real life?
Current oil burners: MB GLK250 BlueTEC, John Deere X758
New ride: MB GLS450 - most stately
Gone but not forgotten: '87 F350 7.3, '93 C2500 6.5, '95 K2500 6.5, '06 K2500HD 6.6, '90 MB 350SDL, Kubota 7510