Engine Hesitates Or Stumbles On Acceleration

Check intake manifold vacuum. Vacuum should be more than 17.7 in. Hg at idle.
Check air filter element.
Check Mass Airflow (MAF) sensor.
Check MAF sensor element for contamination.
Check Engine Coolant Temperature (ECT) sensor.
Check Throttle Position (TP) sensor.
Disconnect injectors in turn and check for equal RPM drop between cylinders.
Check throttle linkage operation.
Check fuel pressure.
Check air passage and vacuum hose installation.
Check for restricted exhaust system.