oh crap... P0430 code

[Special-Ed]

drove to chicago from floriduh. Looks like i am now getting a P0430 code... no prior codes or ces lights prior to this trip.
so i swapped out the right side O2 sensors, the rear one was blackity black... the front looked normal. stupid code comes back. truck runs great, no noticable misses, no noticeable head gasket water leaks, no noticable problems. no vacuum leaks that i can tell...

for 1300 highway miles she ran strong... tool around chicago bam code....
at highway speeds i notice i get no codes... but if i run the cook county forest preserve roads at 45-50 bam get a code...

florida no codes... chicago codes...

im swapping out the plugs and wires in the morning... and air filter.
already cleaned the throttle body/butteryfly, ran it empty and put premium mobil gas in it.

anything else i should look at before i have to pony up 800 bucks to replace the cats?

i do have a cheapy hand held scanner with me, but i see nothing noticable out of spec.

a p0430 is a right bank(passenger side) issue... so that eliminates anything in common with the left bank...

thanx

ed