YIPEEEEE!
CODES CLEARED !!!! Fault codes P0430 and P0420 both now CLEAR!! (cat efficiency below threshold)
I was just going to flush the cats with carb/choke cleaner and sea foam and use same O2 sensors to test if indeed one can clean converter but I broke one of the O2 sensors, the pre-cat from the exhaust manifold closest to the firewall.
WARNING: remove this O2 sensor, all others can be left in. You must remove the passanger windshield cow to reach down in. Removing the coil pack would help too, I didn't. You'll only be able to get an offset O2 wrench/socket on that O2 sensor (like a crows foot). There is not enough room for a standard (long) O2 sensor socket.
So plenty of PB Catalyst penetrating oil on the exhaust manifold studs & nuts helped them come off. SUGGESTION: get a 12mm tap to chase the holes when replacing studs. Also, the advance auto replacement studs did not have a nut flange to wrench on tight so perhaps try napa, carquest, pep boys, or a dealer to get proper studs with 15mm nut flange rather than the round flange with stud having an end slot/flat that you can't get a wrench on by the oil pan. Jerks.
So I cut out the 2 cats, visually they looked pretty good. Flushed with several cans of carb/choke cleaner then poured 3 bottles of sea foam through both directions several times and also filled it with the 2 cans worth of sea foam and held the ends closed while wearing nitrile gloves and rolled the cat around working the fluid to all spots. Then MIG welded the dual converter Y pipe all back together.
On ebay I found 4 O2 sensors for $20 each ,DY745, with only $14 shipping. Great deal.
Been driving a week and no fault codes pending. Going to try and get inspected and emmission tested soon. Been out since June. Not sure my OBD2 will pass since I basically have no first gear due to an AX4N tranny problem. Not sure if I can complete the OBD2 drive cycle if I keep switching down into 2nd gear when I stop. We'll see.
To sum up: replace all O2 sensors first, then try to flush/clean the cats if the new O2 sensors don't do the job. I'm not sure which, if not both solved my problem.
Hope this helps somone out.