So I recently bought a 98 firebird 3.8 and was told it needed a thermostat. Well me being excited over getting the car didn't even think about it having other problems (stupid me) anyways, it's home and I've replaced the thermostat, water pump, some hoses and spark plugs. The oil is fine (no milky color) It doesn't seem to overheat if it's running and just sitting. But when you drive it, it overheats pretty quickly. When you have the radiator cap off while it's running, the coolant blows out everywhere. It's mis-firing on cylinder 3. Is this a messed up head?