1998 Intrigue "random misfire"

[Doctorlen]

After replacing gas tank and fuel filter, when attempting to start the car had a tremendous backfire. prior to this the car ran perfectly. Since this event it is missing and the diagnostic code shows "Random Multiple Misfire". I have tested or replaced the following:
Leads, Plugs, Coils, Ignition Module, MAP Sensor, MAF Sensor, Upper Intake Manifold, Fuel Injectors, Catalytic Converter.
It's driving me nuts. I love this car and it has only 50000 miles.
Any Ideas??

[Doctorlen]

The cause was O2 sensor damaged by backfire. Who would have guessed that one?