The car finally figured out its own problem. I took out my old O2 sensor and was ready to replace the one on the 2.6. But before doing so I tested the voltage on the O2 sensor. Disconnected the black lead and inserted a test wire and with tester connected to ground got ~4.7V on cold start. I was surprised so I checked lambda and found a reading of 30%. So crossing my fingers, I drove around then checked lambda and got a healthy 36%. Adjusted A/F mix and now it's running around 47%.

So 3 things could have happened; sludge blocked the O2 sensor after the seafoam treatment. Poor connection at the O2 sensor. Or something else could have had a bad connection and got cured after wiggling the wires around.

FYI