Toyota Repair: PO420 and PO430, toyota rav4 2002, catalitic converters

Question
Hi Ted , My girlfriend has a Toyota RAV4 2002 about a week ago the check engine light came on, Plus it was running bad it was missing , I checked the code and it had four codes first missfire on # 1 , and #2 was PO420 ,#3 was PO430 and the fourth was the same as #1 . Will the dealer told me to try changing plugs so I did and only 1 code came up it was the same one the missfire code and it still was missing bad so I changed the ignition coil and then the code cleared and ran great nice and smooth , but a few miles down the road the PO420 and PO430 came on so I tried to clear code again and about 25 miles down the road it came on again does this sound like the O2 sensor is bad on Bank 1 and Bank 2 ? And I called about buying one at Autozone just to see if it clears just one then I would find my problem but I would hate to buy one for $450.00 each thats what price they gave me . So what do you think ?  

Answer
The first thing I suggest you do is to call the dealer back and tell them there is a service bulletin from toyota that addresses this problem, it involves reprogramming the on board computer, the warranty period for this is 8yr/80,000 miles, this is a very common problem so have them check with toyota technical information system(TIS)online, it will display the bulletin, I'm surprised that they did not know about this.
The procedure calls for reprogramming the computer and returning the vehicle to the customer, in about 50% of the cases the check engine light will come on again with the same code, if that happens,the catalitic converters get replaced, these also have a warranty period of 8yrs/80,000 miles mandated by the federal emission control warranty(in the US).