alright my cel came on triping the code po420 catalyst below threshold, i changed both o2s and still when i clear it it pops back on? any ideas have after market cat
magna flow?

I've got the exact same cel (420), new cat and o2 sensors as well. As far as I can tell the computer just doesnt like the high flow cats. I have (forget the brand) similar cat to the magnaflow. The cel was fine till the o2 needed to be replaced.
My sugestion is to spend the money on the o2 simulator instead of the actual sensor, might be the only way to rid yourself of this code.

i had that on my 98 it was the cat, replaced it, and good to go. i have a magnaflow on my 05 and never thrown a cel at all since ive owned the car and i scan it every oil change with my scanner just to check

or u have a random gremlin in there not sure xactly what ur problem may be, i had same code went away when i replaced with stock replacement from autozone on my 98