1995 w/3.8 low power with codes indicating o2 leak

[Mordeeb]

I bought this red LX with 45000 miles & almost showroom clean. Didn't take long to find coolant weeping from top engine cover/heads somewhere. Water pump had been replaced, thermostat solid. Oil is fine, not burning coolant, etc. CODES 181, 186, 189 indicating fuel balance compensating for a potential 02 leak. While troubleshooting with the big black book the codes have changed to 172 &176 and no start crank. I have reset the computer back to the first code trio and driven the car. Would someone be able to point me right at something?