[Jrs3800]

Very possible to have a bad cat... also very possible to have a bad O2 that may be flat lining.... The PCM will not flag the O2 until its literally Flat Dead...

Would be good to get a Scan Tool on this car and see what the voltage swing is as well as the cross currents... This car will have a 4 wire heated O2, AC Delco AFS-75, the normal life is 60,000 miles or so then the rate can start to drop off...

I'd say clean the MAF with MAF Cleaner, Have the exhaust system back pressure checked like stated... Checking that O2 is also important...

If you were closer I could scan the car...lol