'97 T-Bird Check Engine light on

My '97 T-Bird, 4.6 Engine, check engine light came on. Had it checked and it shows the following:

Code: P0430
Catalyst efficiency low-bank 2
explanation: oxygen sensors monitor the catalytic converters ability to store oxygen. Probable causes:
1. catalylic converter defective (failure possibility due to #2,3,&4)
2. engine misfiring or not in running condition
3. large vacuum leak
4. engine oil leakage into exhaust valve guide seals, piston rings

Has anyone on here had this problem and where would you suggest starting to correct it? I know it is not number 2 because the car is running great. I see no signs of leakage either. The car is not skipping...running good. Any ideas? Any help is appreciated.

Thanks, Darrell

Have a local muffler shop do a back pressure test on your catalytic converter bank2 (drivers side).