1997 Ford Thunderbird 1997 Thunderbird won't run correctly

I have a 1997 Ford Thunderbird, approx. 122,000 miles, 4.6L V8, Automatic, 2 wheel drive. Car has been maintained well.

It lost passing power on the freeway but made it home. Got it home and tried to restart it and it cranked excessively for about 40 seconds before turning over. When it finally started, it died after putting it in gear and pressing on the accelerator. Also, the Service Engine Soon light came on. It starts fine when it is cold, but after warming up, the rpms drop to less than 100, when it finally dies and is very hard to restart.

I rented an OBD-II code reader from the local auto parts store, brought it home and got codes P-0172 and P-0173. Had the codes deciphered at the auto parts store and it told me that the car was running rich. I was told to replace the o2 sensors, clean the MAF, replace the air filter, spark plugs, and to use injector cleaner. I have done all of this and still the same problems, and the same codes.

What could this be?