P0430 error code

[98TransAmWs-6]

Okay the p0430 error code popped up after I got my coolant sensor fixed and exhaust adjusted at a shop. What would cause this? The exhaust system is obx lts and y-pipe ,high flow cats, and slp loudmouth. My exhaust is only 1 month old. So how could my cats be clogged? At higher rpms it back fires or sounds like it but I don't see any smoke. Any help would be appreciated.

[Jay Dee]

I have had this issue myself a few times. Once it was bad 02 sensors that weren't reading properly behind the cats throwing that code. The other time it was actually a bad spark plug the caused the fuel trims to change enough that I got a backfire sound and an occasional mis-fire. Just replaced and it worked fine.

[Jay Dee]

I have had this issue myself a few times. Once it was bad 02 sensors that weren't reading properly behind the cats throwing that code. The other time it was actually a bad spark plug the caused the fuel trims to change enough that I got a backfire sound and an occasional mis-fire. Just replaced and it worked fine.