I have a 2007 Silverado 1500 WT, 189000 miles, The check engine light came on. Has Autozone read the code. P420. Took a rubber mallet and beat on both CATS for 5 minutes with RPM at 3000. Cleared the codes. Check engine light came back on at 55 miles. Bought a set of Catalytic converters from CARPARTS.COM. Installed the new cats and cleared the codes. The light came back on after 15 miles. Bought a set of sensors from CARPARTS.COM. reset the codes. Light came back on after 13 miles. I took my truck to Chevrolet Dealer and they said that I needed OEM sensors. The installed the new sensors. Light came back on after 20 miles. Took it back to the dealer and they said I needed OEM cats. Cost plus installation was 3200, I declined. Installed a double set of non-foulers in the after cat sensors. the light came back on after 27 miles. I have no clue what to try next? Can it be BAD new Catalytic Converters from CARPARTS.COM