I had the exhaust manifold removed to replace the gaskets. Shortly afterward the engine started to surge a, bit like fuel starvation. Intermittent at first then on a long trip it became bad until the car stalled out. It seemed like fuel flow and having had issues with the pumps previously, I replaced both but on another trip the car started doing it again.

Car has 306k on the odometer and O2 sensor is original. No other issues except that the plug wires had not been seated properly on the plugs and had been arcing. Wires show signs of some damage but are now seated properly. Car runs smoothly until the intermittent surge starts which is a long time between instances. Exhaust smells very rich when idling.

Any thoughts and suggestions are appreciated.