Ok I have a 07 AWD with 57k on it and the last few weeks its been throwing a flashing SES P0300. I know the bank 1 one cats bad because for a year its been throwing a P0420. Whats weird is verified with a Dashhawk it seems to misfire like crazy on 3 always and ONLY under heavy load WOT. I thought this was because the bank one cat was clogged, but I notice on occasions cyl 8 was missing as the same time as 3. I have replaced plugs ngktr6 gapped at .35, factory wires, swapped injectors and coil packs, checked for vaccum leaks, pulled valve covers and no signs of broken springs. Fuel trims are fine on both banks, no oil or coolant loss, I am seing Knock(5 degrees atmost) and hearing clicking which sounds like a skipping bike chain only on heavy load starting around 4k rpms. The truck dosnt seem to be losing any power though, but im lost at this point.