Engine Surges While Cruising

Check intake manifold vacuum. Vacuum should be more than 18.9 in. Hg (1.8L), or 17.7 in. Hg (2.0L), at idle.
Check Throttle Position (TP) sensor.
Check oxygen sensor.
Check for normal Vehicle Speed Sensor (VSS) signal to Engine Control Module (ECM).
Ensure Engine Control Module (ECM) terminal voltages are okay.
Check throttle linkage operation.
Check air filter element.
Check fuel system pressure.
Check for restricted exhaust system.