P0430 code and truck not running

[shaggs_zerog]

HI there, I have an 03 Ex 4.0L SOHC (flex fuel) which won't staying running. I have the CEL codes read and only code that came up is P0430, bank 2 cat eff. below limit. The truck would either stall right after starting or it'll run at idle and stall once i hit the gas.

Any suggestions on what it could be?

 

[shaggs_zerog]

I replaced the main/rear cat converter, and all 4 O2 sensors. That took care of my CEL problem and truck is running smooth for the most part, still need to replace the 2 smaller cat converters. Anyone know where I can get them cheap?