Lack Of Power

Check induction system. Check for air leaks downstream of throttle valve. Inspect duct between mass airflow meter and throttle body.
Check throttle valve for binding and proper adjustment. Ensure throttle valve opens completely.
Ensure fuel pump is okay. Check fuel pressure and pressure regulator. Check for leaks or restrictions in fuel line.
Check injector operation by unplugging connectors one at a time. Engine RPM should drop noticeably. Check opening duration. Check injectors for leaks.
Ensure mass airflow meter filament is not broken and burn-off function is working.
Check turbo and Automatic Performance Control (APC) systems for proper operation.
Check coolant temperature sensor operation.
Ensure electrical harness, connectors and wires are not broken or loose. Check all input signals to ECU.