I have a 6.0l vortec and have knock retard 5 degrees, at high speeds or uphill it bogs. When let go of gas and getting back on it starts to go. Changed sparkplugs 41-962, sparkplug wires, fuel pump, fuel filter, air filter, o2 sensors. It's stock, never been updated so would the 0.04 gap have issue with the original 0.06 gap. I'm thinking sparkplug or fuel injectors or cats, I don't think ignition coils are bad and maf works and other sensors look good.