my k5 has been sitting for a couple month and now will idle but once i give it gas it breaks up and back fires. it is definitly getting way too much gas cause i can smell and see the fog coming out of the exhaust and the air filter. what could be some of the issues i just replaced o2 sensor and spark plugs it ran rich before i let it sit but didnt break up any help or guesses fuel regulator, thermostat, cap ?