Code 430 keeps appearing in my 1999 Camaro SS. I have new cats, what gives

Question

I installed SLP long tube headers about 5 years ago. The headers came with cats and it passed
smog that year. Two years later, it failed the smog check, showing code 430. So I replaced
the cats with some that were supposed to be carb legal. It then passed the test. Now two years
later, the code reappears. Does anyone make cats for my application that will work? I just don't know what else to do. Can anyone out there help me?

Mark