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I have done them all myself as well as all 4x O2 sensors. I did learn not to buy the cheapest crap out there as they fail over time. (not much time at all either) I found someone that did long tube headers and removed their primaries and sold them for a good deal. OEM equipment is better, but way too pricey unless you get a deal. I did the exhaust from the headers to the exhaust tip and still got p0430 codes. I had OEM replacements for the primaries and I bought Magnaflow for the secondaries from amazon.

For clarification:
Are you saying you installed OEM replacements 'post-headers'* along w/ Magnaflow for the secondaries THEN got the p0430 code??
*Stock exhaust manifolds OR aftermarket headers = shorties or long-tubes?

Have heard UpRev may help overcome a p0430 code w/ aftermarket exhaust systems...thoughts?