Have a 86 chevy K10 with 305 during the last snow storm it began running rough, stumbling and stalling at traffic lights. I know its not the gas as I use the same gas in my car. I had the carb taken off, cleaned, adjusted etc. also changed plugs wires etc. Still rrunning rough!!! Ran it yesterday in the yard, with a little pressure on the pedal. Noticed a lot of what seems like Carbon deposits on the snow about two feet from the exhaust. My question is, Could a carbon buildup in the combustion chambers cause this rough running. Also is there any way to clean out the carbon. I seem to remember an old mechanic drizzling a little water down the carb of a vehicle a long time ago to clean out the carbon. Anyone ever tried this? Any other suggestions???