Here's a curiosity for y'all. Occasionally at highway speeds, I've had one a random misfire, no codes and no flashing engine light. My exhaust freaking reeks, not like sulfur (rotten eggs) but of a somewhat fuel-ish smell, and my MPGs have gone from a combined 17.6 to a combined 15.9 Leading me to think that it may the catalytic converter, a fuel delivery issue or a wonky coil. The plugs are new a week ago, it's happened less but only once since. Usually uphill and acceleration. I'm not sure what else to think at this point. I know my water pump is failing, the fan clutch too. But could this cause a misfire? I'll check the fuel pressure today. I ordered Delco 41-103s and new coils, as it's been hard starting lately. What do you GMTNation folks think, I'm curious.