Why waste your own money on sensors? The cats are covered under warranty and their replacement is free. P0420 and P0430 codes are not due to the O2 sensors. They indicate that the cats are unable to perform as they should.

Steve

98 Contour SE Sport 2.5 Duratec ATX The wifey's car 89 Taurus SHO - 246K miles 94 SHO ATX - 190K 1997 F-150 5.4L ATX - The Workhorse 150K. ANY THREAD WITH "OMG" or "WTF" ETC IN THE TITLE WILL BE IGNORED!