Engine Hesitates/Poor Acceleration

Check for clutch slipping or brakes dragging.
Check O2 sensor(s).
Check for vacuum leaks (oil filler cap, oil dipstick, hose connections, PCV hose, PCV valve and EGR system).
Check air filter.
Check airflow meter, coolant temperature sensor, air temperature sensor and throttle position sensor.
Check for leakage or clogging between air filter and turbocharger inlet, and between turbocharger outlet and cylinder head (if equipped).
Check secondary ignition system performance and ignition timing.
Verify timing belt alignment
Check engine compression and valve clearance.
Ensure fuel system functions properly (pump, lines, filter and pressure regulator).
Check for clogged fuel injectors.
Check variable induction system (if equipped).
Check power to ECU via fusible links, fuses and EFI main relay.
Check injection signal circuit.