Next step is a pressure test of the intake. Also, there is no way to tell whether the turbos are "working" or not just starting the car and running it with no load. You will hear them spinning, but they will spin under any condition unless they're seized.
1) Pressure test intake
2) Check operation of vacuum control system for wastegates. This includes vacuum pump output (at least 20inHg vacuum), all hoses from the pump to the solenoids, and operation of the wastegate acutators themselves.
E92 335i/6MT Dinan Stage 3: intercooler, oil cooler, intake, flash, exhaust, LW dual-mass flywheel.
Vishnu PWM methanol custom trunk mount, Diffsonline 3-clutch Salisbury custom diff, Ohlins Road and Track coilovers, Vorshlag camber plates, much more...
E28 M5 w/ buncha stuff, R171 SLK350