Seafoam is not likely to help. It rarely does, except for a few rare instances of carbureted engines, and usually 2-strokes.
Instead of adding oily water with naptha for $8 a can or so (Seafoam) add some fresh, LOW octane gasoline. Lower octane contains fewer additives and is more volatile (thus the lower octane rating) and that volatility can help undo the damage from the water in Seafoam and stale fuel (more than 60days old) in the tank.
Check the heater circuit for OČ 2/2. The heater element may be open, and a post-cat sensor usually needs the supplemental heat to generate a meaningful signal until the cat gets really hot.