No check for boost leaks first.
You can do this by using a leak down tester and a drilled and tapped pvc cap so that you can twist the leak down tester into. Attach that at the turbo inlet and then apply air pressure to the desired boost level. Go by the gauge on the leakdown tester not the car gauge you don’t actually have enough volume of air to create a large amount of boost. spray down the vacuum lines, couplers, piping welds, gaskets on the intake side back side of the compressor housing (huge leaks usually) all that and check for air leakage with soapy water. bubbles indicate air leaking.