I replaced my engine at 52,000 miles because of chewed up rod bearings (#6 was completely gone). The replacement motor was used. Since the motor was installed, I've put 10,000 miles on it but have had a misfire in cyl #5 (only at idle) and a P0430 code the entire time. All of the electronic components, sensors, and fuel delivery components were swapped from the original motor and there were no codes or misfire present with the old motor. I've changed the plugs, wires, fuel filter, IMRC, and tested the DPFE (it tested good).
Other than the occasional rotten egg smell (which existed before the motor swap), it runs strong and gets 24mpg around town and 31mpg on the highway.
I'm guessing the misfire is causing the P0430 since it's for bank #2, the same bank as cyl #5. If I clear the codes, the CEL will flash indicating misfire almost immediately, but it takes about 50 miles of driving for the P0430 to show up.