Originally Posted by texasssei
I listened to the cat it has a slight raddle so more then likey the cat has gone out again
Unfortunately. Time for you (or your favorite shop) to break out the welding equipment.
DTC P0420, "Catalyst System Efficiency Below Threshold" means that your catalytic converter is doing a poor job of breaking down the ozone-depleting and smog-generating molecules in your exhaust. Thus, you won't pass your state'* emissions testing while this code is set.
Rarely, it can mean that your downstream (post-cat) O2 sensor has gotten tired, but since you've replaced both, that rules that out.
This is where we would normally suggest that you check for exhaust leaks, but if your cat is rattling, that'* a telltale sign that its internals are in pieces.