My mechanic pressure tested the cooling system with up to 15 lbs. of pressure. He said it held the pressure but I am not sure how long he tested it. I'll see if I can get him to do a compression test. Could a leak flow one way (into the radiator), and not the other (into the cylinder)? I would think so because of the higher pressures of the combustion process versus the lower pressure of the cooling system. And once I "depressurize" the engine when I turn it off, the coolant may be seeping into the cylinders causing the cold start misfires. I am just speculating at this point but I guess the logical next step would be a compression test. Much obliged for the advice!