I've been chasing down a general poor performance in my car. Ive checked it with T-link and it doesn't have codes, and runs fairly well but never perfectly smooth, sounds like intermidant misses or miss firing. Also I was looking for a small radiator leak when doing a cooling system flush i noticed air bubbles flowing into the overflow tank. Following this lead the coolant system becomes pressurized after just a few minutes of running. The oil is not contaminated and the water/anti-freeze does smell like gas(noticed this today too) I'm assuming its a head gasket but wouldn't it smoke or contaminate the oil? How would i check to make sure before i year it down. Could it be something more extensive, like a cracked head or block? I have no idea how long its been like this, I've had cooling problems for almost a year now.