Hi. Got a turbo issue with my legacy b4. The first stage turbo spools up but no power getting to engine. I’ve had it checked and the turbo works. Had the pipes, exhaust, hoses all checked but knowone seems to know why. Any advice would be welcome. 

A smoke test would rule out a intake leak , otherwise boost is controlled by the solenoids , a lot of vac lines and the actuators/ wastegates .

Unfortunately all i know about the twin turbo vac lines and solenoids is that they're complicated. But a check for split vacuum pipes leading from the turbo actuators and outlet neck to the solenoid box and inlet manifold would be doing .

Also worth checking the actuator arm on the bigger turbo isn't loose , it should be difficult to pull the wastegate open with your fingers .

Is there any ecu codes ?