Engine Runs Rough On Deceleration

Check intake manifold vacuum. Vacuum should be more than 17.7 Hg at idle.
Perform switch monitor function test. See SYSTEM/COMPONENT TESTS article in the ENGINE PERFORMANCE section.
Check air filter element.
Ensure ECM terminal voltages are okay. See PIN VOLTAGE CHARTS article in the ENGINE PERFORMANCE section.
Verify idle speed is correct.
Verify correct throttle body dashpot adjustment.
Check engine coolant temperature sensor.
Check oxygen sensor.
Verify Throttle Position (TP) sensor has correct adjustment and resistance value. See ADJUSTMENTS article in the ENGINE PERFORMANCE section.
Check Mass Airflow (MAF) sensor.
Check for leaking fuel injectors.