Unfortunately, gas does not dissolve carbon that is the byproduct of combustion. I had a piece of carbon come loose in Moab last year and you would have sworn the engine was coming apart until it passed out the exhaust valve. I�ve seen inside several under 30K mile Isuzu engines (I have 2 VX intakes in my garage) and the black coating that builds up is thick and hard and should be removed - it will not go away with over the counter products although they can help minimize it.